GHM GREISINGER GMH 3531 User manual

H70.0.01.6C-04
GHM GROUP - Greisinger
GHM Messtechnik GmbH | Hans-Sachs-Str. 26 | 93128 Regenstauf | GERMANY
Tel.: [phone] | [email protected] | www.greisinger.de
as of version V1.2 GMH 3531
WEEE-Reg.-Nr. DE 93889386
Operating Manual
Handheld pH / ORP-Meter

Please carefully read these instructions before use!

Please consider the safety instructions!

Please keep for future reference!

H70.0.01.6C-04 Operating Manual GMH 3531 page 2 of 18
Content
1GENERAL NOTE......................................................................................................................................................3
2SAFETY......................................................................................................................................................................3
2.1 INTENDED USE.......................................................................................................................................................3
2.2 SAFETY SIGNS AND SYMBOLS................................................................................................................................3
2.3 SAFETY GUIDELINES..............................................................................................................................................3
3PRODUCT SPECIFICATION..................................................................................................................................4
3.1 OPERATION AND MAINTENANCE ADVICE..............................................................................................................4
4HANDLING................................................................................................................................................................5
4.1 DISPLAY ................................................................................................................................................................5
4.2 PUSHBUTTONS.......................................................................................................................................................5
4.3 CONNECTIONS .......................................................................................................................................................6
4.4 POP-UP CLIP...........................................................................................................................................................6
5START OPERATION................................................................................................................................................7
6PRINCIPLES OF THE MEASUREMENTS...........................................................................................................7
6.1 PHMEASUREMENT ................................................................................................................................................7
6.2 ORP MEASUREMENT .............................................................................................................................................7
6.3 RHMEASUREMENT................................................................................................................................................8
6.3.1 Manual input of pH value (and temperature)................................................................................................8
6.3.2 Automatic input of pH value from preceding pH measurement.....................................................................8
6.4 PHELECTRODE ......................................................................................................................................................8
6.4.1 Design............................................................................................................................................................8
6.4.2 Further Information.......................................................................................................................................8
6.4.3 pH electrode suggestions...............................................................................................................................9
6.5 CALIBRATION OF PHMEASUREMENT....................................................................................................................9
6.5.1 How to prepare calibration buffers of standard GPH series (capsules) .......................................................9
6.5.2 Automatic temperature compensation during calibration.............................................................................9
6.5.3 How to carry out calibration .......................................................................................................................10
7CONFIGURATION.................................................................................................................................................11
8OUTPUT ...................................................................................................................................................................13
8.1 SERIAL INTERFACE..............................................................................................................................................13
8.2 ANALOG OUTPUT.................................................................................................................................................13
9INPUT ADJUSTMENT...........................................................................................................................................14
10 GLP ...........................................................................................................................................................................14
10.1 CALIBRATION INTERVAL (C.INT) .......................................................................................................................14
10.2 CALIBRATION STORAGE (READ CAL) ...............................................................................................................14
11 REAL TIME CLOCK („CLOC“) ..........................................................................................................................14
12 ACCURACY CHECK / ADJUSTMENT SERVICE............................................................................................15
13 ERROR AND SYSTEM MESSAGES ...................................................................................................................15
14 RESHIPMENT AND DISPOSAL..........................................................................................................................15
14.1 RESHIPMENT.......................................................................................................................................................15
14.2 DISPOSAL INSTRUCTIONS ...................................................................................................................................16
15 SPECIFICATION....................................................................................................................................................16
16 NOTES A: TEMPERATURE INFLUENCE ON PH BUFFER SOLUTIONS..................................................17
17 NOTES B: PREPARATION OF PH BUFFER SOLUTIONS.............................................................................17

H70.0.01.6C-04 Operating Manual GMH 3531 page 3 of 18
1 General Note
Read this document carefully and get used to the operation of the device before you use it. Keep this
document within easy reach near the device for consulting in case of doubt.
Mounting, start-up, operating, maintenance and removing from operation must be done by qualified, specially
trained staff that have carefully read and understood this manual before starting any work.
The manufacturer will assume no liability or warranty in case of usage for other purpose than the intended
one, ignoring this manual, operating by unqualified staff as well as unauthorized modifications to the device.
The manufacturer is not liable for any costs or damages incurred at the user or third parties because of the
usage or application of this device, in particular in case of improper use of the device, misuse or malfunction
of the connection or of the device.
The manufacturer is not liable for misprints.
2 Safety
2.1 Intended Use
The device is designed for measuring pH and ORP potentials with the help of adequate electrodes. The
electrode is connected via BNC-socket.
Please note: Different electrode types are needed for pH and ORP measurements.
It is possible to connect a temperature probe (Pt1000, banana plugs) additionally. This enables an automatic
temperature compensation (ATC) for pH, rH and mVH measurements and displaying the media’s
temperature.
The safety requirements (see below) have to be observed.
The device must be used only according to its intended purpose and under suitable conditions.
Use the device carefully and according to its technical data (do not throw it, strike it, …)
Protect the device from dirt.
2.2 Safety signs and symbols
Warnings are labeled in this document with the followings signs:
DANGER
Caution! This symbol warns of imminent danger, death, serious injuries
and significant damage to property at non-observance.
Attention! This symbol warns of possible dangers or dangerous
situations which can provoke damage to the device or environment at
non-observance.
Note! This symbol point out processes which can indirectly influence
operation or provoke unforeseen reactions at non-observance.
2.3 Safety guidelines
This device has been designed and tested in accordance with the safety regulations for electronic devices.
However, its trouble-free operation and reliability cannot be guaranteed unless the standard safety measures
and special safety advises given in this manual will be adhered to when using the device.
1.
Trouble-free operation and reliability of the device can only be guaranteed if the device is not subjected
to any other climatic conditions than those stated under "Specification".
If the device is transported from a cold to a warm environment condensation may cause in a failure of
the function. In such a case make sure the device temperature has adjusted to the ambient temperature
before trying a new start-up.

H70.0.01.6C-04 Operating Manual GMH 3531 page 4 of 18
2.
If there is a risk whatsoever involved in running it, the device has to be switched off
immediately and to be marked accordingly to avoid re-starting.
Operator safety may be a risk if:
- there is visible damage to the device
- the device is not working as specified
- the device has been stored under unsuitable conditions for a longer time.
In case of doubt, please return device to manufacturer for repair or maintenance.
3.
When connecting the device to other devices the connection has to be designed most thoroughly as
internal connections in third-party devices (e.g. connection GND with protective earth) may lead to
undesired voltage potentials that can lead to malfunctions or destroying of this device and the connected
devices.
This device must not be run with a defective or damaged power supply unit.
Danger to life due to electrical shock!
4.
Do not use these products as safety or emergency stop devices or in any other
application where failure of the product could result in personal injury or material damage.
Failure to comply with these instructions could result in death or serious injury and
material damage
5.
This device must not be used at potentially explosive areas!
The usage of this device at potentially explosive areas increases danger of deflagration,
explosion or fire due to sparking.
6.
This device is not constructed for use in medical applications.
7.
The analog output is designed to output the current measured value and may only be
used in a non-process-relevant manner in applications where no personal or material
damage can occur.
3 Product Specification
3.1 Operation and maintenance advice
1. Battery operation:
If and ‘bAt’ are shown in the lower display the battery has been used up and needs to be replaced.
However, the device will operate correctly for a certain time. If ‘bAt’ is shown in the upper display the
voltage is too low to operate the device; the battery has been completely used up.
The battery has to be taken out, when storing device above 50 °C.
We recommend taking out battery if device is not used for a longer period of time.
After recommissioning the real-time clock has to be set again.
2. Mains operation with power supply
When using a power supply please note that operating voltage has to be 10.5 to 12 V DC.
Do not apply overvoltage!! Cheap 12V-power supplies often have excessive no-load voltage.
We, therefore, recommend using regulated voltage power supplies.
Prior to connecting the power supply to the mains make sure that the operating voltage stated
at the power supply is identical to the mains voltage.
The external supply must not have a galvanic connection to the measurement medium, as this
can influence the measurement and thus lead to measurement errors.
Trouble-free operation is guaranteed by our power supply GNG10/3000.
3. Treat device and sensor carefully. Use only in accordance with above specification. (do not throw, hit
against etc.). Protect plug and socket from soiling.
4. Display values for damaged electrode cable or if no pH or ORP electrode has been connected:
If no electrode is connected or the connection cable is damaged the display will nevertheless show mV,
pH or rH values. Please note that these values can never be correct measuring results!

H70.0.01.6C-04 Operating Manual GMH 3531 page 5 of 18
4 Handling
4.1 Display
1
Main display: pH value,
ORP value (mV, mVH),
rH value
2
Display elements to show minimum/maximum/
memorized measuring value
3
Arrows to selected measuring unit
4
Warning signal (low battery or recalibration prompt)
5
atc arrow: indicates if temperature sensor is
connected and therefore automatic
temperature compensation is active (only
for ‘pH’, ‘mVH’ and ‘rH’ measuring mode)
6
stab arrow: indicates stable measuring value
7
cal arrow: indicates a running calibration
(at operation mode ‘pH’).
8
Secondary display: temperature value
9
No function
4.2 Pushbuttons
On / off key
Set/Menu:
press for 2 sec. (menu): invoke configuration menu
press shortly:
at ‘pH’, ‘rH’ and ‘mVH’: manual temperature input
(if no temperature probe is connected)
additionally at ‘rH’: manual input of pH value
+
min/max when taking measurements:
press shortly: min. or max. meas. value so far will be
displayed
press for 2 sec.: the min. or max. value will be deleted
Configuration:
to enter values, or change settings
Store/Quit
-Measuring:
with Auto-Hold off: hold and save current measuring value (‘HLD’ is displayed)
with Auto-Hold on: start new measuring, It is finished , when “HLD’ shows in display
(refer to chapter 7)
-Set/Menu: confirm settings, return to measuring
CAL: (only at mode ‘pH’)
press shortly: display of electrode state rating –additional short presses: show actual
calibration data
press for 2 sec: start pH calibration
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
pHmV mV
H
rH
ATC ok CAL AL Logg pH
mbar

H70.0.01.6C-04 Operating Manual GMH 3531 page 6 of 18
4.3 Connections
interface: connection for galv. Isolated interface adapter
(accessory: GRS 3100, GRS3105 or USB3100)
BNC socket: connection of pH or ORP electrode
(glass electrodes or combination electrodes)
Banana sockets:
Connection of Pt1000 temperature probe
Electrodes with integrated temperature sensor:
the banana plug is connected from outside
Separately lead through reference electrode:
it is connected from inside
Power supply: additional d.c.connector (internal pin Ø 1.9
mm) for external 10.5-12V direct voltage supply.
4.4 Pop-up clip
Handling:
•Pull at label “open” in order to swing open the pop-up clip.
•Pull at label “open” again to swing open the pop-up clip further.
Pop-up clip closed
Pop-up clip at position 90°
Pop-up clip at position 180°
Function:
• The device with a closed pop-up clip can be plainly laid onto a table or attached to a belt, etc.
• The device with pop-up clip at position 90° can be set up on a table, etc.
• The device with pop-up clip at position 180° can be suspended from a screw or the magnetic holder
GMH 1300.
Device attached to a belt
Device set up on a table
Device suspended from
magnetic holder
GMH 1300

H70.0.01.6C-04 Operating Manual GMH 3531 page 7 of 18
5 Start Operation
Connect electrodes, turn device on via key.
After segment test the device displays some configuration:
if zero point or slope correction is active
(p.r.t chapter 7 „Configuration“ and 0„
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit

H70.0.01.6C-04 Operating Manual GMH 3531 page 8 of 18
Input adjustment“)
Remove protective cap from electrode. (Attention: Cap should contain KCL 3 M or storage solution)
After that the device is ready for measuring.
6 Principles of the measurements
6.1 pH measurement
The pH value specifies the acid or alkaline behavior of aqueous solutions.
Solutions with a pH values below 7 are acid (the more below 7 the more acid), values higher than 7 mean
alkaline and pH = 7 means neutral.
The pH value is the negative common logarithm of the hydrogen ion activity (this is often approximately
equal to the concentration of dissolved hydronium ions):
  󰇡󰇛󰇜󰇛󰇜
 
 󰇢with 󰇛󰇜: concentration of dissolved hydronium ions in mol/l
󰇛󰇜: activity coefficient (normally lower than 1)
The abbreviation “pH” stands for pondus Hydrogenii (Latin pondus: “weight“; Hydrogenium: “hydrogen“).
pH values should always be measured and saved together with the temperature of the solution:
i.e. pH 5.87; 22.8 °C.
Reason: The pH values of most liquids are depending on temperature.
The pH measurement is highly precise but also very sensitive. The measured signals are very weak (high
resistance), especially if measured in low-ion media. Therefore it is very important that:
- disturbances (electrostatic charge, etc.) are prevented.
- a stable value is reached by slow stirring.
- contact plugs are kept clean and dry.
- the electrode shaft is not submersed for a longer period (exception: special water-proof types).
- the electrode is calibrated often enough (see below). The needed calibration frequency depends on
the used electrode and application and varies between once every hour to once in several weeks.
- A suitable electrode is chosen. Please refer to chapter 6.4
6.2 ORP measurement
The ORP potential (also known as reduction potential or ORP) is a measure of the oxidizing or reducing
potential of the measured media compared to the standard hydrogen electrode.
This potential is often used in swimming pools to rate the disinfectant effect of chlorination. Also for aquarium
keepers the ORP value is an important parameter, because fishes need ORP values within specified
boundaries to live. Drinking water purification, water monitoring and industrial applications are some further
fields where the ORP value is of importance.
The measurement is done with a common silver chloride electrode (reference system with 3-molar
potassium chloride solution). The measured value can be directly displayed (mode mV) or converted to
“reference system: standard hydrogen electrode” and temperature compensated at mode mVH.
There is no calibration comparable with that of the pH measurement. However, the electrode’s capability can
be checked with ORP test solutions (for example GRP 100).
Suitable ORP electrodes: e.g. GE 105 BNC

H70.0.01.6C-04 Operating Manual GMH 3531 page 9 of 18
6.3 rH measurement
The rH value is a calculated value of a pH and an ORP measurement. For example it is used to describe the
anti oxidative effect of food. This is a measure for the ability of food to reduce harmful free radicals.
To measure the rH value of a solution, proceed as follows:
6.3.1 Manual input of pH value (and temperature)
You can set the value for pH and temperature (if no temperature sensor is connected) manually. Press key
shortly and set the temperature value with keys and . Press shortly again and enter the pH
value. Confirm with .
6.3.2 Automatic input of pH value from preceding pH measurement
It is important that the pH and ORP electrodes are in sound condition and that they are cleaned and
dried well before they are inserted to the solution.
First place pH and ORP electrode and temperature probe in the solution and stir carefully.
1. Measuring pH value:
Connect the pH electrode and temperature probe to the GMH 5550.
Then set device to pH measuring mode and calibrate electrode if necessary
(p.r.t. chapter 6.5 Calibration of pH measurement and chapter 7 Configuration).
Measure the pH value of the solution and store the measured value with . Do not turn off the
device until the tH measurement is finished. If the device is turned off the saved pH value is deleted
and has to be set manually for the following rH measurement.
2. Get the rH value:
Connect ORP electrode and set device to rH measuring mode. The main display shows the
calculated rH value of the solution, the secondary display shows the prior measured pH value and
the temperature alternatingly.
6.4 pH electrode
6.4.1 Design
In most cases so-called combination electrodes are used. That means that
all needed elements are integrated in a single electrode (including
reference electrode).
Sometimes even a temperature sensor is integrated.
The picture on the right shows an electrode without temperature sensor.
There are several design types for the diaphragm, but generally said it is
the connection between electrolyte and the measured solution. A blockade
or soiling of the diaphragm is often the reason for the electrodes idleness
and erratic behavior.
The glass membrane has to be treated with care. The hydrated gel layer
forms on the surface of the glass membrane, which is of highest importance
for the measurement. The electrode has to be kept wet to preserve the
hydrated gel layer (see below).
6.4.2 Further Information
pH-electrodes are wear parts which need to be replaced, if the values
required can no longer be kept even after thorough cleaning and recovery
or the electrode signal gets to slow. The actual lifetime of an electrode
depends highly on the chemical or mechanical stress it is subjected to.
Please take into account that there are several materials that are in
aqueous solutions aggressive to glass; other chemicals may react with the
KCl-solution in the electrode thus causing blockades in the diaphragm.
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
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CAL
min
Set
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1 2 3
4 5 6
ON
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CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
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CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
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CAL
min
Set
Menu Quit

H70.0.01.6C-04 Operating Manual GMH 3531 page 10 of 18
Examples:
- with solutions containing protein, like they are used on the medical and biological sector, KCI may result in
the denaturation of the protein.
- coagulated varnish
- solutions with a relatively high concentration of silver ions
Any material depositing on the measuring membrane or the diaphragm will influence the measurements and
have to be removed at regular intervals. This can be done by means of automatic cleaning equipment.
Electrodes have to be stored in a way that they are kept wet. An adequate solution is to
store them with suitable protective cap filled with KCl 3 M. Please consider also the
instructions in the electrodes manual!
6.4.3 pH electrode suggestions
Different applications require different electrodes
1. Measurements in low-ion media (rain water, aquarium water, VE-waters)
GE 104 BNC (as of 20 µS/cm)
2. Sea water aquariums
Standard pH electrodes with 3mol KCl (GE 100 BNC, GE 117)
3. Swimming pools
Standard pH electrodes with 3mol KCl (GE 100 BNC, GE 117)
4. Soil checks
Glass electrodes with several diaphragms (GE 101 BNC); use insertion mandrel!
5. Electroplating, some paints and lacquers
Glass electrode GE 151 BNC
6. Cheese, fruit, meat
Insertion electrode (GE 101 BNC or GE 120 BNC).
When taking measurements in cheese, milk and other high-protein products use special cleaning agent to
clean electrode. (pepsin solution - GRL 100).
Standard cleaning: apply 0.1 molar HCl-solution for at least 5 minutes or protein cleaning agent.
The average service life of an electrode is 8 to 10 months but may be increased to 2 years if electrode is well
maintained and treated carefully. We regret not being able to give a more detailed information as this is
highly dependent on the individual case of application.
6.5 Calibration of pH measurement
The electrode data of pH electrodes are subject to fluctuation due to ageing and manufacturing tolerances.
Therefore it is necessary to check the calibration with buffer solutions before measurements take place. If
deviations are too large, a recalibration is necessary. See also chapter 10 GLP.
Buffer solutions are liquids with an accurate pH-value. The following buffers can be used for calibration:
- Technical buffer series PHL (ready to use, pH 4.01, pH 7.00 und pH 10.01)
- Standard series GPH (buffer capsules to be mixed with water pH 4.01, pH 7.00 and pH 10.01)
- DIN series CAL dIn (pH 1.68 (A), pH 4.01 (C), pH 6.87 (D), pH 9.18(F) und pH 12.45(G))
- Arbitrary buffer CAL Edit (neutral buffer ranging from 6.5 ... 7.5pH)
Service life of a buffer solution is limited and will be further reduced unless the electrodes are
properly rinsed and dried when changing over the solutions. This may even result in incorrect
calibration! We recommend to use new buffer solution for calibration, as far as possible, and to
rinse with deionized or distilled water.
6.5.1 How to prepare calibration buffers of standard GPH series (capsules)
See notes B.
6.5.2 Automatic temperature compensation during calibration
Both the signal of the pH-electrode and the pH-buffer are depending on temperature. If a temperature probe
is connected, the temperature influence of the electrode is compensated automatically during measuring as
well as during calibration. Otherwise enter actual buffer temperature as accurate as possible (see below).
When working with the standard or DIN-buffer series, the influences of buffer temperature are also
compensated. If buffers are entered manually, make sure to enter the pH-values of the buffers at the relevant
temperature to ensure optimum calibration of the device.

H70.0.01.6C-04 Operating Manual GMH 3531 page 11 of 18
6.5.3 How to carry out calibration
Please note: the calibration can only carried out at a temperature range of 0 - 60°C !
If you have not yet done so set device to measuring mode ’pH’. Make sure that either the 1-, 2- or 3- point
calibration (whichever is required) and desired buffer series (PHL, GPH, dIn or Edit) the has been activated
(further information in chapter 7 „Configuration“).
Carefully remove electrode safety cap (Attention! Contains 3 mol KCl!).
Rinse electrode with distilled water and dry it carefully.
How to start calibration: press key for 2 seconds.
The display will prompt you to measure the first calibration solution.
You can abort calibration at any time by pressing key. In such a case the last calibration before this one
remains valid.
1. Calibration point 1: ‘Pt. 1’
*1)
Place electrode and temperature probe
(if any) in the neutral solution stirring
gently.
(For 1-point calibration: solutions with
arbitrary pH value (e.g. pH 4) can be uses)
As soon as the measured pH value got
stable the next calibration step will be
displayed.
No temperature sensor:
manual input of
temperature of buffer 1
Use or to enter the temperature of
the buffer solution.
Use to confirm the value; the next
calibration step is displayed.
If 1-point calibration is chosen the calibration is already done at this point, the display shows the electrode’s
state rating.
2. Rinse electrode in distilled or deionized water, dry electrode
3. Calibration point 2: ‘Pt. 2’ (only for 2- or 3- point calibration)
*1)
Place electrode and temperature probe
(if any) in the second buffer solution (e.g.
for standard series this is: pH 4.0 or pH
10.0) and stir gently.
As soon as the measured pH value got
stable the next calibration step will be
displayed.
No temperature sensor:
manual input of
temperature of buffer 2
Use or to enter the temperature of
the buffer solution.
Use to confirm the value; the next
calibration step is displayed.
If 2-point calibration is chosen the calibration is already done at this point, the display shows the electrode’s
state rating.
4. Rinse electrode in distilled or deionized water, dry electrode
5. Calibration point 3: ‘Pt. 2’ (only for 3- point calibration)
Please note: both, an alkaline and acid calibration point are needed for a 3-point calibration.
*1)
Place electrode and temperature probe
(if any) in the third buffer solution (e.g. for
standard series this is: pH 10.0) and stir
gently.
As soon as the measured pH value got
stable the next calibration step will be
displayed.
No temperature sensor:
manual input of
temperature of buffer 3
Use or to enter the temperature of
the buffer solution.
Use to confirm the value; the next
calibration step is displayed.
Calibration has finished, the display shows the electrode’s state rating.
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit

H70.0.01.6C-04 Operating Manual GMH 3531 page 12 of 18
*1) In case of manual buffer selection (CAL Edit) use or to enter pH value of the used solution. If
solutions from the standard and DIN series are used their pH value will be automatically detected.
Use to confirm the value; the next calibration step is displayed.
Error messages of pH calibration:
Neutral buffer not permissible
- Wrong buffer solution
- Buffer solution defective
- Electrode defective
Always use neutral buffer as first solution
(exception: 1 point calibration)
Use new buffer solution
Clean electrode and calibrate again, if error occurs
again -> replace electrode
Slope is too low:
- Buffer solution defective
- Electrode defective
Use new buffer solution
Replace electrode
Slope is too high:
- Buffer solution defective
- Electrode defective
Use new buffer solution
Replace electrode
Incorrect calibration temperature
Calibration can only be done at 0…60 °C
Permissible electrodes’ data:
Asymmetry: ±55 mV
Slope: -62 ... -45 mV/pH
7 Configuration
Some menu points depend on current device settings.
To change device settings, press „Menu“ for 2 seconds. This will activate the configuration menu (main
display: “Set”). Pressing „Menu“ changes between the menus points, pressing jumps to the
referring parameters, which can be selected with key .
The parameters can be changed with or . Pressing „Menu“ again jumps back to the main
configuration menu and saves the settings. "Quit" finishes the configuration and returns to standard
measuring operation.
Pressing “menu” and “store” at the same time for more than 2 seconds will reset the
device to factory defaults
If no key is pressed for more than 2 minutes the configuration will be aborted. All changes will
not be saved!
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
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CAL
min
Set
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1 2 3
4 5 6
ON
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CAL
min
Set
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1 2 3
4 5 6
ON
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CAL
min
Set
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1 2 3
4 5 6
ON
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CAL
min
Set
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1 2 3
4 5 6
ON
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CAL
min
Set
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1 2 3
4 5 6
ON
OFF max
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CAL
min
Set
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1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit

H70.0.01.6C-04 Operating Manual GMH 3531 page 13 of 18
Menü
Parameter
Werte
Bedeutung
bzw.
Set Configuration: General configurations
Input: Selection of measured variable
Arrow „rH“
rH value measurement
Arrow „mV“
mV value measurement (REDOX or ORP)
Arrow „mVH“
mV value measurement referring to standard hydrogen system
Arrow „pH“
pH value measurement
Resolution pH: Resolution of ph display
0.1 .. 0.01
tenth pH … hundredth pH
Calibration: Select number of calibration points
1-Pt
1-point (only offset calibration, slope = -59.2mV/pH)
2-Pt
2- point (neutral + another one)
3-Pt
3- point (neutral + one acid + one alkaline buffer)
Calibration: Select buffer series
GPH
Technical Buffer series: GPH-Capsules (pH7, pH4, pH 10)
PHL
Technical liquid buffer series: PHL (pH7, pH4, pH 10)
dIn
DIN 19266 buffer series pH 1.68(A), pH 4.01(C), pH 6.87(D), pH
9.18(F), pH 12.45(G)
Edit
Arbitrary buffer, manual input
Calibration: Calibration reminder period (factory setting: off)
1 …365
Calibration reminder period (in days)
oFF
No calibration reminder
Unit t: Select temperature unit
°C:
All temperatures in degree Celsius
°F:
All temperatures in degree Fahrenheit
Auto Hold: Auto measuring value identification
on
Auto measuring value identification Auto Hold
oFF
Standard hold function on key press
Auto Power-Off: Select power-off delay
1...120
Power-off delay in minutes. Device will be automatically switched off
as soon as this time has elapsed if no key is pressed/no interface
communication takes place.
oFF
Automatic power-off function deactivated (continuous operation)
Universal Output
oFF
Interface off -> minimal power consumption
SEr:
Serial interface activated
dAC:
Analog output activated
01,11..91
Base address for serial interface communication
Set Corr: Input adjustment
Zero adjustment / offset of voltage measurement
oFF
No zero adjustment for voltage measurement
-10 … 10 mV
Offset of voltage measurement in mV
Slope adjustment of voltage measurement
oFF
No slope adjustment for voltage measurement
-5.00 … 5.00%
Slope correction of voltage measurement in %
Zero adjustment / offset of temperature measurement
oFF
No zero adjustment for temperature measurement
-5.0 … 5.0°C
Offset of temperature measurement in °C
Slope adjustment of temperature measurement
oFF
No slope adjustment for temperature measurement
-5.00 … 5.00%
Slope correction of temperature measurement in %
Set Clock: Settings for real time clock
HH:MM
Clock: set time hours:minutes
YYYY
Year: set year
TT.MM
Date: set date day.month
rEAd CAL: Read calibration data:
p.r.t. chapter 10.2 Calibration storage (rEAd CAL)
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit

H70.0.01.6C-04 Operating Manual GMH 3531 page 14 of 18
8 Output
The output can be used as serial interface (for USB 3100, USB 3100 N, GRS 3100 or GRS 3105
interface adapters) or as analog output (0-1V).
If none of both is needed, we suggest to switch the output off, because battery life then is extended.
When operating with external supply or connected interface and measurement at solutions
with earth connection, there may appear distortions or deviations of the measuring. In case of
doubt disconnect supply/interface.
The same is valid for the analogue output: Depending how the output is connected (e.g. even
without isolation), in case of doubt do not measure in solutions with earth contact.
8.1 Serial Interface
By means of the serial interface and a suitable electrically isolated interface adapter (USB 3100, USB 3100 N,
GRS 3100 or GRS 3105) the device can be connected to a computer for data transfer.
With the GRS 3105 up to 5 devices of the GMH3xxx- series can be connected to one interface (see also
manual of GRS 3105). As a precondition the base addresses of all devices must not be identical, make sure to
configure the base addresses accordingly (refer menu point “Adr.” in chapter 7).
To avoid transmission errors, there are several security checks implemented e.g. CRC.
The following standard software packages are available:
GSOFT3050: Operation and read out of logger function, data display in diagrams and tables
GMHKonfig: Software for a comfortable editing of the device
EBS 20M / 60M: 20-/60-channel software to display the measuring values
In case you want to develop your own software we offer a GMH3000-development package including:
a universally applicable Windows functions library ('GMH3000.DLL') with documentation that can be used
by the most programming languages. Suitable for Windows XP™, Windows Vista™, Windows 7™
Programming examples Visual Basic 4.0™, Delphi 1.0™, Testpoint™
The device has 2 channels:
- Channel 1: actual-value-channel pH, mV or rH and base address
- Channel 2: temperature value
The unit of all transmitter values (including measuring / boundary values) is the unit of
corresponding displayed values.
(e.g. temperature is displayed in °C -> temperature value is also transmitted in °C)
8.2 Analog output
Keep in mind not to connect low-resistive loads to the output, otherwise the output value
will be wrong and battery life is decreased. Loads above approx. 10kOhm are uncritical.
The signal conditioning instrument used must be galvanically isolated from the measured
medium and any external supply voltage used for the measuring device.
An analog voltage 0-1 V can be connected at the universal output connector (mode: “Out dAC”).
The analog output cannot be scaled.
Unit
0V output signal
1V output signal
pH
0.00 pH
14.00 pH
mV / mVH
-2000 mV
2000 mV
rH
0.0 rH
70.0 rH
If the displayed value goes beyond the fixed value, the output voltage will be 1 V.
If the displayed value falls below the fixed value, the output voltage will be 0 V.
In error case (Err.1, Err.2, etc.) the output voltage will be slightly higher than 1 V.
plug wiring:
GND
+Uout
Attention!
The 3rd contact has to be left floating!
Only stereo plugs are allowed!

H70.0.01.6C-04 Operating Manual GMH 3531 page 15 of 18
9 Input adjustment
The zero point and slope of each measuring inputs can be adjusted with the parameters offset (“OFFS”) and
scale (“SCAL”).
A reasonable adjustment presumes reliable references (e.g. ice water, controlled precision water bath, etc.).
If the inputs are adjusted (i.e. offset and scale are different from default settings) the device will shortly
display “Corr” after turned on.
Default setting for offset and scale are ‘off’ = 0.0, i.e. inputs are not changed.
Zero point correction:
Displayed value = measured value –OFFS
Zero point and slope correction:
Displayed value = (measured value –OFFS) * (1 + SCAL / 100 )
(Displayed value °F = (measured value °F - 32°F - OFFS) * (1 + SCAL / 100 ) )
10 GLP
GLP (Good Laboratory Practice) includes regular check of devices and accessories. For pH measurements it
is highly important to ensure correct pH calibration. The device provides the following functions to help with
this.
The usage of the GLP functions is only reasonable if the electrode is not changed. Although all data is stored
in the device, it refers to the particular electrode.
10.1 Calibration interval (C.Int)
You can input the interval after which the device reminds you to recalibrate.
The interval times should be chosen according to the application and the stability of the electrode.
“CAL” flashes on the display as soon as the interval has expired.
10.2 Calibration storage (rEAd CAL)
The last 16 calibrations are stored with results and date and can be read out.
Display calibration data:
Historical calibration data can be comfortably read out via PC software GMHKonfig and GSOFT3050 or
displayed directly at the device:
Press for 2 seconds
The display will show:
oder (configuration level)
Press several times until this is
displayed:
read cal. = “read calibration data”
Press shortly: switch between
- U.ASY = asymmetry voltage in mV
- SL. 1 = slope acid in mV/pH *1)
- SL. 2 = slope alkaline in mV/pH *1)
- date+time display of data set
or
Change between the different calibration data sets
Quit calibration data sets display
*1) 1-point calibration: slope acid = slope alkaline = 59.16mV/pH is assumed
2-point calibration: slope acid = slope alkaline = determined slope
3-point calibration: slope acid and slope alkaline are determined separately
11 Real Time Clock („CLOC“)
The real time clock is used for chronological assignment calibration points. Please check the settings when
necessary.
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit

H70.0.01.6C-04 Operating Manual GMH 3531 page 16 of 18
12 Accuracy Check / Adjustment Service
You can send the device to the manufacturer for adjustment and inspection.
Calibration certificate - DKD certificate - official certifications:
If the measuring instrument is supposed to receive a calibration certificate, it has to be sent to the
manufacturer (declare test levels, e.g. -20; 0°C; 70°C).
If the device is certificated together with a suitable sensor very high overall accuracies are possible.
Basic settings can only be checked and –if necessary –corrected by the manufacturer.
A calibration protocol is enclosed to the device ex works. This documents the precision reached by the
production process.
13 Error and System Messages
Display
Description
What to do?
No display or
confused
characters,
device does not
react on keypress
Battery empty
Replace battery
Mains operation: wrong voltage or polarity
Check power supply, replace it when necessary
System error
Disconnect battery and power supplies, wait
shortly, then reconnect
Device defective
Return to manufacturer for repair
Err.1
Measured value above allowable range
Check: Measuring value not within sensor range?
-> measuring value to high!
Sensor defective
Return to manufacturer for repair
Err.2
Measured value below allowable range
Check: Measuring value not within sensor range?
-> measuring value to low!
Sensor defective
Return to manufacturer for repair
Err.7
System error
Return to manufacturer for repair
Value extremely out of measuring range
Check: Value not within sensor range?
>CAL<
CAL flashing in
display
Either preset calibration interval has
expired or last calibration is not valid
Device has to be calibrated!
Neutral buffer not permissible
Wrong buffer solution
Always use neutral buffer as first solution
(exception: 1 point calibration)
Buffer solution defective
Use new buffer solution
Electrode defective
Clean electrode and calibrate again, if error occurs
again -> replace electrode
Slope is too low
Electrode defective
Replace electrode
Buffer solution defective
Use new buffer solution
Slope is too high
Electrode defective
Replace electrode
Buffer solution defective
Use new buffer solution
Incorrect calibration temperature
Calibration can only be done at 0…60 °C
If “bAt” is flashing, the battery will be exhausted soon. Further measurements are possible for short time. If
“bAt” is displayed continuously the battery is ultimately exhausted and has to be replaced. Further
measurements aren’t possible any more.
14 Reshipment and Disposal
14.1 Reshipment
DANGER
All devices returned to the manufacturer have to be free of any residual of measuring media
and/or other hazardous substances. Measuring residuals at housing or sensor may be a risk for
persons or environment

H70.0.01.6C-04 Operating Manual GMH 3531 page 17 of 18
Use an adequate transport package for reshipment, especially for fully functional devices.
Please make sure that the device is protected in the package by enough packing materials.
14.2 Disposal instructions
Batteries must not be disposed in the regular domestic waste but at the designated collecting
points.
The device must not be disposed in the unsorted municipal waste! Send the device directly to us
(sufficiently stamped), if it should be disposed. We will dispose the device appropriate and
environmentally sound.
Private end users in Germany have the possibility of dropping off the device at the municipal
collection centre. Batteries must be removed beforehand!
15 Specification
Measuring ranges
pH
0,00 ... 14,00 pH
ORP / mV
-1999 … 2000 mV
Relating to hydrogen system: -1792 .. +2207 mVH(bei 25°C, DIN 38404)
rH
0,0 … 70,0 rH
Temperature
-5,0 ... +150,0 °C, Pt1000
23,0 ... 302,0 °F
Accuracy
pH
±0,01 pH
ORP / mV
±0,1% FS
Temperature
±0,2 K (in the range of -5,0…100,0°C)
Working conditions
-20 to 50 °C; 0 bis 95 % r.F. (non condensing)
Storage temperature
-20 to 70 °C
Connections
pH, ORP
BNC- socket, additional connection for reference electrode: 4mm banana socket
Temperature
Pt1000 via 4 mm banana socket
Interface
Serial interface (3.5mm jack) can be connected to USB or RS232 interface of a
PC via electrically isolated interface adapter USB3100, USB 3100 N, GRS3100
or GRS3105 (see accessories) or analog output 0-1V
(max. permitted connection length = 2m)
external supply
d.c. connector (diameter of internal pin 1.9 mm) for external 10.5-12V direct
voltage supply. (suitable power supply: GNG10/3000)
Input resistance
pH, OPR
>1012 Ohm
Display
4 digit 7-segment (main and secondary display) with additional symbols
pH calibration
Automatic
1 -, 2- or 3-point calibration,
either DIN 19266-buffer or technical buffer GPH / PHL
Manual
1 -, 2- or 3- point calibration
GLP
calibration storage
adjustable calibration intervals (1 to 365 days, CAL warning after expiration)
Additional functions
Min / max / hold / auto-hold
Housing
Break-proof ABS housing
Protection class
Front side IP65
Dimensions
Weight
without BNC connector 142 x 71 x 26 mm (L x B x H) BNC connector at the
devices front end: approx. 13 mm long, about 170 g incl. battery
Power supply
Current consumption
9V battery (included in scope of supply), external d.c. supply
< 1 mA (Out = Off)
Change battery indicator
Automatically if battery exhausted and ’ bAt ’
Auto-off-function:
Device will be automatically switched off if no key is pressed/no interface
communication takes place for the time of the power-off delay. The power-off
delay can be set to values between 1and 120 min.; it can be completely
deactivated.
Directives and standards
The instruments confirm to following European Directives:
2014/30/EU EMC Directive
2011/65/EU RoHS
Applied harmonized standards:
EN 61326-1 : 2013 emissions level: class B
emi immunity according to table A.1 and 3 1)
Additional fault: <1%
EN IEC 63000 : 2018
1) = In the case of conducted interference radiation in the range of 5 - 50 MHz,
interference of the analog output can occur at the level of the maximum
output voltage range.

H70.0.01.6C-04 Operating Manual GMH 3531 page 18 of 18
16 Notes A: temperature influence on pH buffer solutions
GPH buffer capsules for 100 ml buffer solution
Capsules for do-it-yourself mixing –unopened capsules can be stored a long time (approx. 3 years)
T [°C]
10
20
25
30
40
GREISINGER GPH 4.0
3.99
3.99
4.01
4.01
4.03
GREISINGER GPH 7.0
7.06
7.01
7.00
6.99
6.98
GREISINGER GPH 10.0
10.18
10.06
10.01
9.97
9.89
GREISINGER GPH 12.0
12.35
12.14
12.00
11.89
11.71
PHL buffer solutions in dosing bottles 250 ml
Buffer solutions are ready for use, with dosing volume of 20 ml - 25 ml
T [°C]
10
20
25
30
40
GREISINGER PHL 4,0
(pH 4.01 +/- 0.015 @25°C)
4.02
4.00
4.01
4.01
4.01
GREISINGER PHL 7,0
(pH 7.00 +/- 0.015 @25°C)
7.06
7.02
7.00
6.99
6.97
GREISINGER PHL 10,0
(pH 10.01 +/- 0.030 @25°C)
10.18
10.07
10.01
9.97
9.89
17 Notes B: preparation of pH buffer solutions
General information on pH buffer solutions
The actual characteristic curve of pH electrodes deviates from the ideal characteristic. Thus the electrodes have to
be calibrated before initial operation and thereafter at regular intervals to get accurate measuring values.
At least a 2-point calibration is required to get the parameters ‘offset’ and ‘slope’. Two different buffer solutions are
necessary for this.
A 1-point calibration only affects the ‘offset’ whereas ‘slope’ is assumed to be the ideal value of -59.2 mV/pH. A
device calibrated only at 1 point assures only accurate measuring values at a range close to the buffer value.
Buffer capacity β
The pH value of a buffer solution changes only very little when small amounts of acids or bases are added. The
buffer capacity β and the dilution influence dpH are values to measure this capability. The buffer capacity β is the
amount of a strong acid or base that has to be added to 1 liter of the buffer solution in order to change its pH value
by 1. The dilution influence dpH is the change of the pH value of the buffer solution when it is diluted with pure
water at a ratio of 1 to 1.
Typical values for buffer capacity and dilution influence are: β = 0.03; dpH = 0.05
Please consider when choosing buffer solutions: date of expiry
Unopened and well stored buffer capsules (GPH) can be stored for a very long time in contrast to ready to use or
self prepared buffer solutions. Caution with alkaline buffers: they age comparatively fast if opened (i.e. at air). The
buffer gets more acid, because carbon dioxide from air is dissolved.
How to prepare calibration buffers of standard GPH series (capsules)
1. Fill 2 plastic bottles with 100 ml distilled water each.
2. Open pH 7 capsule (green) carefully (turn one half of the capsule while pulling and make sure not to
spill any of the powder); put content (including both capsule parts) into one of the bottles.
3. Put content of pH 4 capsule (orange) (or pH 10, blue) and both capsule parts into a second bottle..
The capsule shell will color the liquid in the respective color:
orange = pH4.01; green = pH7.00; blue = pH10.01
Make sure to prepare buffer solutions in time as they can only be used after at least 3 hours.
Shake well before use.