GREISINGER GMH 3750 User manual

H49.0.02.6C-10
GHM GROUP - Greisinger
GHM Messtechnik GmbH | Hans-Sachs-Str. 26 | 93128 Regenstauf | GERMANY
Tel.: [phone] | [email protected] | www.greisinger.de
as of version 1.6 operating manual GMH 3750
Precision thermometer
for Pt100 4-wire temperature probes
WEEE-Reg.-Nr. DE 93889386
GMH 3700 Series
Pt100 Thermometer
Hochpräzision / High-Precision

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CONTENTS
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 SCOPE OF SUPPLY ..................................................................................................................................................4
3.2 OPERATION AND MAINTENANCE ADVICE..............................................................................................................4
4HANDLING................................................................................................................................................................5
4.1 DISPLAY ................................................................................................................................................................5
4.2 BASIC OPERATION.................................................................................................................................................5
4.3 CONNECTIONS .......................................................................................................................................................5
4.4 POP-UP CLIP...........................................................................................................................................................6
5START OPERATION................................................................................................................................................7
6CONFIGURATION...................................................................................................................................................7
7REMARKS TO SPECIAL FEATURES ..................................................................................................................8
7.1 DISPLAY RESOLUTION...........................................................................................................................................8
7.2 AVERAGE FILTER („T.AUG“)................................................................................................................................8
7.3 ALARM („AL.“) .....................................................................................................................................................8
7.4 USER SENSOR CURVE ('LIN USER').......................................................................................................................9
7.5 REAL TIME CLOCK („CLOC“)...............................................................................................................................9
8OPERATION OF LOGGER.....................................................................................................................................9
8.1 STORING SINGLE MEASUREMENTS („FUNC-STOR“) .............................................................................................9
8.2 AUTOMATIC RECORDING WITH SELECTABLE CYCLE TIME „FUNC CYCL“.......................................................10
9OUTPUT ...................................................................................................................................................................11
9.1 SERIAL INTERFACE..............................................................................................................................................11
9.2 ANALOGUE OUTPUT –SCALING WITH DAC.0 AND DAC.1................................................................................12
10 INPUT ADJUSTMENT........................................................................................................................................12
10.1 ZERO DISPLACEMENT ('OFFSET').....................................................................................................................12
10.2 SCALE CORRECTION ('SCALE').........................................................................................................................12
10.3 CALIBRATION SERVICES..................................................................................................................................12
11 PROBE CONNECTION......................................................................................................................................12
12 SOME BASICS OF PRECISION TEMPERATURE MEASURING..............................................................13
13 FAULT AND SYSTEM MESSAGES.................................................................................................................14
14 RESHIPMENT AND DISPOSAL.......................................................................................................................14
14.1 RESHIPMENT ....................................................................................................................................................14
14.2 DISPOSAL INSTRUCTIONS.................................................................................................................................14
15 SPECIFICATIONS...............................................................................................................................................15

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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.
2 Safety
2.1 Intended Use
The GMH 3750 is a precision thermometer for the measurement of the temperature with exchangeable 4-
wire Pt100 temperature sensors. With high resolution and precision temperature values can be measured
from -200 to 850 °C.
The device is to be protected against wetness and soiling and has to be stored and operated only within the
permissible environmental conditions and connection data (see “Specification”).
2.2 Safety signs and symbols
Warnings are labelled 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.
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.
DANGER

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
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 the 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.
3 Product Specification
3.1 Scope of supply
The scope of supply includes:
device with 9V battery block
Operation manual
3.2 Operation and maintenance advice
Battery operation
If ‘bAt’ is 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.
•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.
Trouble-free operation is guaranteed by our power supply GNG10/3000.
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.
Treat device and sensor carefully. Use only in accordance with above specification. (do not throw, hit
against etc.). Protect plug and socket from soiling.
To disconnect temperatur sensor plug do not pull at the cable but at the plug.
When connecting the probe the plug will slide in smoothly if plug is entered correctly.
Selection of Output-Mode: The output can be used as serial interface or as analogue output. This
choice has to be done in the configuration menu.
_DANGER
_DANGER
DANGER
DANGER

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4 Handling
4.1 Display
1 Maindisplay: Currently measured temperature
2 Secondary display: Display of min, max or hold values
Special display elements:
3Min/Max/Hold: shows if a min., max. or hold value is
displayed in the auxiliary display
4“Offset“ arrow: indicates that zero point offset is activated
5„Corr“ arrow: indicates that a scale correction is activated
6„Logg“ arrow: Shown if logger function is selected,
flashes if cyclic logger is running
7„Alarm“ arrow: Flashes if alarm is present
4.2 Basic Operation
On / Off
+
min/max at measure:
press short: shows the min./max. value
press again: hides min./max. value
press 2 sec.: clears particular value
Function only during configuration:
Selection of menu-parameter
Set/Menu:
press short: invokes configuration menu
Store/Quit:
press short: hold-function, the last measuring
value will be held in the secondary
display.
at active logger: invokes logger functions
at menu: acknowledge setting, return to
measurement
4.3 Connections
Output: Connection for el. Isolated interface adapter
or for analog output (please refer to chapter
9)
Probe connection: 4 pole Mini-DIN-Socket, for Pt100
4-wire probes
Power supply: the mains adapter socket is located at the left side of the device.
1 2 3
4 5 6
ON
OFF max Tara
Storemin
Set
Menu Quit
1 2 3
4 5 6
ON
OFF max Tara
Storemin
Set
Menu Quit

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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

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5 Start Operation
Connect Temperature probe, turn on device via key.
After segment test the device displays some configuration:
• If the logger function is not off the time of the integrated clock will shortly be displayed.
• If a zero point adjustment was carried out the display shows shortly „nuLL Corr“.
After changing the battery the clock-setting menu is activated automatically (‚CLOC‘). Check the clock
and adjust, if necessary (p.r.t. chapter 6).
After that the device is ready for measuring.
6 Configuration
To change device settings, press Menu (key 4) for 2 seconds. This will call the configuration menu (main
display: „SEt“ or “rEAd LoGG”).
Pressing key Menu changes between the menus, pressing ( (key 3) jumps to the referring parameters,
which can be selected with key ( (key 3).
The parameters can be changed with (key 2) or (key 5).
Pressing Menu again jumps back to the main configuration menu and saves the settings.
Quit (key 6) finishes the configuration and returns to standard measuring operation.
Menu(*1)
Parameter/Values(2*)
Meaning
p.r.t.
‚Menu‘

or 
Read Logg: single value-logger read out
(only when data existing! Please refer to chapter 12)
8
Set Configuration: Generic Settings
°C:
All temperature values are in degrees Celsius
*
°F:
All temperature values are in degrees Fahrenheit
0.1° / 0.01°:
Resolution 0.1° / 0.01°
*
7.1
Auto:
Resolution is selected automatically
E.751
characteristic curve according to EN60751
*
7.4
USEr
User sensor curve (Predefined to EN60751 values,
changeable by software GMHKonfig)
-2.50...2.50°C /
-4.50...4.50°F
Zero correction
*
10.1
oFF:
Zero displacement inactive (=0.0°)
-2.000...2.000:
Scale correction [in %]
*
10.2
oFF:
Scale correction factor inactive (=0.000)
1...30:
Average filter (period in seconds)
*
7.2
oFF:
Average filter inactive
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 or no interface
communication takes place
oFF
Power-off function inactive (continuous operation)
oFF:
No output function
9
SEr:
Output is serial interface
dAC:
Output is analogue output
01,11..91
Base address of device for interface communication
9.1
-200..850°C /
–328...1562°F
Zero point of analogue output: Temperature at
which the analogue output potential should be 0V
9.2
1 2 3
4 5 6
ON
OFF max
Store
CAL
min
Set
Menu Quit

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-200..850°C /
-328...1562°F
Scale of analogue output : Temperature value at
which the analogue output potential should be 1V
9.2
Set Alarm: Setting of Alarm Function
On / No.So
Alarm on with horn-sound / Alarm on without horn-
sound
7.3
OFF
no alarm function
-200°C ...AL.Hi
Min alarm rail (not when AL. oFF)
AL.Lo ... 850°C
Max alarm rail (not when AL. oFF)
Set Logger: Setting of Logger Function
CYCL
Cyclic: logger function cyclic logger
*
8
Stor
Store: logger function individual value logger
OFF
No logger function
0:01... 60:00
Cycle time of cyclic logger [minutes:seconds]
*
8
Set Clock: Einstellen der Echtzeituhr
HH:MM
Clock: Setting of time hours:minutes
7.4
YYYY
Year
TT.MM
Date: day.month
(*) If the logger memory contains data already, the menus/parameters marked with (*) can not
be invoked! If these should be altered the logger has to be stopped and the memory has to
be cleared before!
Hint: Restoring of ex-works settings
The settings will be set to the settings ex works, if keys ‘Set‘ and ‘Store‘ are pressed simultaneously
for more than 2 seconds.
7 Remarks To Special Features
7.1 Display Resolution
Standard setting: 'Auto', i.e. the device automatically switches over to the optimum resolution between .01°
and 0.01°.
If temperatures to be measured are near the switching threshold, a fixed resolution may be better, e.g. for
easy manual recording. In such a case please set the optimum resolution to the desired value.
7.2 Average filter („t.AuG“)
The filter forms the arithmetic floating average over the entered time. The displayed value will be
correspondingly slower in this case.
7.3 Alarm („AL.“)
There are three possible settings:
Alarm off (AL. oFF), on with horn sound (AL. on), on without horn sound (AL. no.So).
Following conditions will display an alarm, when the function is activated (on or no.So):
-Value is below lower (AL. Lo) or above upper alarm rail (AL.Hi).
-Sensor error
-Low battery (bAt)
-Err.7: System error (always with sound)
In case of an alarm and when polling the interface the “prio”-flag is set in the returned message.

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7.4 User Sensor Curve ('Lin USEr')
By means of this function besides the standard conversion of resistance to temperature following
EN60751(Lin E.751) also other curves can be used. The user sensor curve can be read and edited by the
configuration software GMHKonfig. The standard setting ex works is also set to the EN60751 data. The
curve is defined by a table with two columns (input resistance[Ohm]/output temperature [°C]) with 50 rows.
Info: the sensor curve following EN60751 uses the international temperature scale ITS90 and following
formulas:.
Temperatures < 0°C:
Rneg(T) := 100 · [1 + 3.9083·10-3·T –5.775·10-7·T2 –4.183·10-12·(T –100)·T3]
Temperatures >= 0°C:
Rpos(T) := 100 · (1 + 3.9083·10-3·T –5.775·10-7·T2)
Please notice: Temperature measurements with the user sensor curve are allowed only within the
temperature range which has been used to generate the user sensor curve.
Measuring with activated user sensor curve beyond the checked temperature range may lead to
larger errors. Therefore the sensor curve acc. to EN 60751 (Lin E.751) has to be used for
temperature measurements beyond the checked temperature range.
7.5 Real Time Clock („CLOC“)
The real time clock is used for the logger function: Recorded values are also containing the point of time,
when they were measured. Please check the settings when necessary.
If the battery was replaced the referring menu ‚CLOC‘ will automatically be started
8 Operation Of Logger
The device supports two different logger functions:
„Func-Stor“: manual recording via keypress “Store” (key 6).
„Func-CYCL“: automatic recording with the selected recording interval/cycle
The logger records 1 measurement result each time
The data set consists of: - measuring value at time of recording
- time and date of recording
For the read out and evaluation of the data the software GSOFT3050 (V1.7 or higher) has to be used. The
software also allows easy configuration and starting of the logger.
When the logger is activated (Func Stor or Func CYCL) the hold function is no longer available, key 6 is
solely used for the operation of the logger functions.
8.1 Storing Single Measurements („Func-Stor“)
a) Record Measuring:
If the logger function “Func Stor” was activated (see chapter 6“Configuration”), up to 99 measuring data
sets can be recorded manually.
Press shortly: Data set will be recorded (“St. XX” will be shown shortly. XX is the number of the
data set)
If the logger memory is full, the display will show:
b) Viewing Recorded Measurings:
Stored data sets can be either read out via PC Software GSOFT3050, or be viewed in the display directly.
Press for 2 seconds: The display will show:
Please note: ”rEAd Logg” only appears, if there are already data stored! If memory is empty, the
configuration menu will show.
Press shortly: Changing between measuring value and date+time of data set
or
Changing between the data sets
Exit logger data display

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c) Clear recorded measurings:
If there are already data sets stored, these can be deleted via the store key:
Press for 2 seconds: Calling of clear-Menu
Change selection by: or :

Clear nothing (cancel menu)

Clear all recordings

Clear the last recording
Stores the settings
8.2 Automatic Recording With Selectable Cycle Time „Func CYCL“
If the logger function “Func CYCL” was activated (see chapter 6 “Configuration”), and the logger was started,
it automatically records data sets at intervals of the selected logger cycle time
The logger cycle time is selectable from 1s to 60min (see chapter 6 “Configuration”).
Max. number of measurings: 16384
a) Starting a recording:
press for 2 seconds: the recording will be started.
Each recodring is signales with a short diplay of ‘St.XXXXX’. XX is the number of the data set.
If the logger memory is full, the display will show
b) Stop the recording:
Press for 2 seconds: If a recording is running, the Stop menu will be shown
Change selection by: or :
Do not stop the recording
Stop the recording
Stores the settings
Note: If you try to switch off the instrument in the cyclic recording operation, You will be asked
automatically if the recording should be stopped.
The device can only be switched off after the recording has been stopped!
The Auto-Power-Off-function is deactivated during recording!
c) Clear recorded measurings:
Press for 2 seconds: If logger data are present and the recording was stopped, the
clear menu will be shown
Change selection by: or :
Clear nothing
(cancel menu)
Clear all recordings
Stores the settings

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9 Output
The output can be used as serial interface (for USB 3100, USB 3100 N, GRS 3100 or GRS 3105
interface adapters) or as analogue output (0-1V).
If none of both is needed, we suggest to switch the output off, because battery life then is extended.
9.1 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 6).
To avoid transmission errors, there are several security checks implemented e.g. CRC.
The following standard software packages are available for data transfer:
GSOFT3050: Operating and evaluation software for instruments with integrated logger function
EBS20M/ -60M: 20- / 60-channel software to record and display the measuring values
GMHKonfig: Software for a comfortable configuration of the device (e.g. freeware)
In case you want to develop your own software we offer a GMH3000-development package including
- an universally applicable 32bit Windows functions library ('GMH3000.DLL') with documentation that can
be used by all 'serious' programming languages.
- Programming examples for Visual Studio 2010 (C#, C++), Visual Basic 6.0™, Delphi 1.0™, Testpoint™,
Labview™
In addition to the operation at a PC the device can be operated with the GAM3000-device, to use the alarm
function for simple supervision and controlling applications. Just connect a GAM3000 to the interface,
activate the alarm function of the GMH and the relays output is operating.
Supported interface functions:
code
name / function
code
name / function
0
Read nominal values
201
Read max. display range
3
Read system status
202
Read unit of display
6
Read min. values
204
Read decimal point of display
7
Read max values
208
Read channel count
12
Read ID-no
214
Read scale correction
22
Read min. alarm rail
215
Set scale correction
23
Read max. alarm rail
216
Read zero displacement
32
Read configuration flag
Alarm function: 1, Alarm horn: 3
BitLoggerOn: 50, BitCyclicLogger: 51
217
Set zero displacement
222
Read power –off time
223
Set power –off time
102
Set min. alarm rail
224
Logger: read data cyclic logger
103
Set max. alarm rail
225
Logger: read cycle time (LoGG - CYCL)
160
Set configuration flag (see 32)
226
Logger: set cycle time (LoGG - CYCL)
174
Delete min. value
227
Logger: start recording
175
Delete max. value
228
Logger: read # of data
176
Read min. measuring range
229
Logger: read status
177
Read max. measuring range
231
Logger: read stop time
178
Read measuring range unit
233
Read real time clock (CLOC)
179
Read measuring range decimal point
234
Set real time clock (CLOC)
180
Read measuring type
236
Read logger memory size
194
Set display unit
240
Reset
199
Read measuring type in display
254
Read program identification
200
Read min. display range
260
Logger: read data manual logger
Note: The measuring and display range values read via interface are always in the selected display
unit (°C/°F)!

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9.2 Analogue Output –Scaling with DAC.0 and DAC.1
Note: Analogue output can not be used during logger recordings
With the DAC.0 and DAC.1 values the output can be rapidly scaled to your efforts.
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 ca 10kOhm are uncritical.
If the display exceeds the value set by DAC.1, then the device will apply 1V to the output
If the display falls below the value set by DAC.0, then the device will apply 0V to the output
In case of an error (Err.1, Err.2, no sensor, etc.) the device will apply slightly above 1V to the output.
plug wiring:
GND
+Uout
Attention!
the 3rd contact has to be left floating!
Only stereo plugs are allowed!
10 Input Adjustment
10.1 Zero Displacement ('Offset')
The zero displacement is used to adjust the measuring display for probe deviations.
temperature displayed = temperature measured - offset
Standard setting: 'off' = 0.0°, i.e. no zero displacement will be carried out. Together with the scale correction
(see below) this factor is mainly used to compensate for sensor deviations.
Unless the factor is set to 'off', the offset arrow in the display shows an active zero displacement.*)
10.2 Scale Correction ('Scale')
The scale correction is used to adjust the measuring display for probe deviations. (factor is in %):
displayed temperature[°C] = measured temperature[°C] * (1+Scal/100)
or: displayed temperature[°F] = (measured temperature [°F]-32°F) * (1+Scal/100) + 32°F
Standard setting: 'off' =0.000, i.e. temperature is not corrected.
Unless the factor is set to 'off', the Corr arrow in the display shows an active scale correction.*)
*) The standard curve (Lin E.751) and the user sensor curve (Lin USEr) posses separate correction settings.
10.3 Calibration Services
Calibration certificates –DKD-certificates –other certificates:
If device should be certificated for its accuracy, it is the best solution to return it to the manufacturer.
Only the manufacturer is capable to do efficient recalibration if necessary to get results of highest accuracy!
11Probe Connection
The device is constructed and optimised for the connection of a Pt100 4-wire probe via 4 pole Mini-Din
connectors.
4-wire connection
Figure shows upon probe jack pins
It is also possible to connect an 3- or 2-wire probe to the device. Please observe that in consequence of the
cable and contact resistance an increased measuring fault will occur.
The connection of this probes should be carried out as follows:
3-wire connection
2-wire connection
Pt100

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12Some Basics Of Precision Temperature Measuring
Probe Precision/Device Precision
The device is very precise (please refer to technical data). To be able to use this high precision, the
connected temperature probe has to be as precise as possible, too. The following precision classes are
available as a standard at reasonable prices (Platinum resistor thermometers according to EN60751):
Class Error ranges
B ± (0,3 + 0,005 • | Temperature |)
A ± (0,15 + 0,002 • | Temperature |)
AA (=1/3 DIN) ± (0,1 + 0,0017 • | Temperature |)
1/10 B (=1/10 DIN) ± (0,03 + 0,0005 • | Temperature |)
Error over measuring range
Error over range –50...150°C
For applications demanding higher precision than given by this classes we suggest to adjust the device to
the used probe or to get a calibration certificate for the device combined with the probe.
Attention: if an adjusted or calibrated probe is replaced, also the adjustment or calibration certificate has to
be renewed to maintain the referring overall precision! Be careful when buying third party
temperature probes: Besides the standard EN60751 there are some other obsolete or unusual
standards on the market. If such a probe has to be connected, the user sensor curve (have a
look to the referring chapter) can be used to adjust the instrument!
4-Wire-Measuring
When using resistance thermometers as the Pt100 a quite large measuring error can be caused by inadequate cables
and connections. Using 4wire measuring avoids this kinds of errors mainly caused by unwanted resistances. It is
suggested to use suitable probes and extensions only.
Heat loss caused by probe construction:
Especially when measuring temperatures which deviate very much from the ambient temperature, measuring errors
often occur if the heat loss caused by the probe is not considered. When measuring fluids therefore the probe should be
emerged sufficiently deep and be stirred continuously. When measuring gases the probe should also emerge as deep
as possible in the gas to be measured (e.g. when measuring in channel/pipes) and the gas should flow around the
probe at sufficient flow.
Measuring Surface Temperature
If temperature of the surface of an object has to be measured, one should pay attention especially when measuring hot
(or very cold) surfaces, that the ambient air cools (or heats) the surface. Additionally the object will be cooled (or
heated) by the probe or the probe can have a better heat flow to the ambient temperature as to the objects surface.
Therefore specially designed surface probes should be used. The measuring precision depends mainly on he
construction of the probe and of the physics of the surface itself. If selecting a probe try to choose one with low mass
and heat flow from sensor to handle. Thermally conductive paste can increase the precision in some cases.
Allowable temperature Range Of Probes
Pt100 Sensors are defined over a wide temperature range. Depending on probe materials and sort of sensor (e.g.
hybrid sensors, wire wound resistors...) the allowable temperature ranges have to be considered. Exceeding the ranges
at least causes a wrong measuring, it may even damage the probe permanently!
Often it also has to be considered, that the temperature range is just valid for the probe tube, (plastic-) handles can’t
stand the same high temperatures. Therefore the tube length should be selected long enough, that temperature keeps
low at the handle.
Self Heating
The measuring current of the instrument is just 0.3mA. Because of this comparably low current practically now self
heating effect has to be considered, even at air with low movement the self heating is <= 0.01°C.
Cooling by Evaporation
When measuring air temperature the probe has to be dry. Otherwise the cooling due to the evaporation causes too low
measuring.
0
1
2
3
4
-200 -100 0 100 200 300 400 500 600 700 800
Fehler [°C]
T [°C]
Fehler Gerät und Temperaturfühler
B
1/3B
1/10B
A
0
0,2
0,4
0,6
0,8
1
1,2
-50 -30 -10 10 30 50 70 90 110 130 150
Fehler [°C]
T [°C]
Fehler Gerät und Temperaturfühler
B
1/3
B

H49.0.02.6C-10 User’s Guide GMH 3750 page 14 of 16
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13Fault and System Messages
Display
Meaning
Remedy
Low battery voltage, device will
continue to work for a short time
Replace battery
If mains operation: wrong voltage
Check/replace power supply, if fault continues
to exist: device damaged
Low battery voltage
Replace battery
If mains operation: wrong voltage
Check/replace power supply, if fault continues
to exist device damaged
No display
Or
Weird display
Device does not
react on keypress
Low battery voltage
Replace battery
If mains operation: wrong voltage
Check/replace power supply, if fault continues
to exist device damaged
System error
Disconnect battery or power supply, wait some
time, re-connect
Device defective
Return to manufacturer for repair
----
Sensor error, no sensor connected
Connect sensor to socket
Sensor/cable or device defective
Return to manufacturer for repair
Err.1
Value exceeding measuring range
Check: Is the value exceeding the measuring
range? Temperature too high!
Wrong probe connected
Check probe
Sensor/cable defective
Replace
Err.2
Value below display range
Check: Is the value below the measuring
range? Temperature too low!
Wrong probe connected
Check probe
Sensor/cable defective
Replace
Err.3
Value exceeding display range
Set resolution to 0.1° or Auto
Err.4
Value below display range
Set resolution to 0.1° or Auto
Err.7
System error
Return to manufacturer for repair
14Reshipment and Disposal
14.1 Reshipment
All devices returned to the manufacturer have to be free of any residual of measuring media and
other hazardous substances. Measuring residuals at housing or sensor may be a risk for
persons or environment
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.

H49.0.02.6C-10 User’s Guide GMH 3750 page 15 of 16
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15 Specifications
Supported probes Pt100 4-wires (2-wire possible)
Sensor Curve according to EN60751 or with user-sensor curve (table of 50 rows)
Probe connection 4-pole Mini-DIN socket
Resolution 0,01°C 0,1°C 0,01°F 0,1°F
Measuring Ranges -199,99…199,99 -200,0…850,0 -199,99…199,99 -328,0…1562,0
Precision Device without probe ±1Digit (at nominal temperature)
Range 0.01°C/F ±0.03 °C / ±0.06 °F
Range 0.1°C/F ±0.1 °C / ±0.2 °F
Measuring 4-wire measuring with thermovoltage compensation, measuring current 0.3 mA
Measuring rate: 2 measurements per second
Temperature drift <= 0,002 K per 1K
Nominal temperature 25 °C
Ambient condition -25 ... +50 °C (-13 …+122 °F), 0 to 95 %RH (not condensing)
Storage temperature -25 ... +70 °C (-13…158 °F)
Output: 3.5 mm audio plug, stereo
output configurable to serial interface or to analog output
serial interface: via optically isolated interface adapter USB 3100, USB 3100 N, GRS 3100 or
GRS 3105 (accessory) connectable to PCs with USB- or RS232-interfaces.
analog output: 0..1V, freely scaleable (resolution 13bit,accuracy 0.05% at nominal temperature),
cap. load <1nF
Power Supply: 9V-Battery (included) as well as additional d.c. connector (diameter of internal pin 1.9
mm) for external 10.5-12V direct voltage supply.
(Suitable power supply: GNG10/3000)
Power Consumption Output off approx. 0,90 mA
Output = serial interface approx. 1,15 mA
Analog output approx. 1,25 mA
Display: Two 4 ½ digits LCD’s (12.4mm and 7 mm high), additional segments
Pushbuttons: 6 membrane keys
Min-/Max-Memory Both the max. and the min. value will be memorised.
Holdfunction Press button to store current value.
Automatic-Off-Function Device will be automatically switched off if not operated for longer time (adjustable
from 1 ... 120 min)
Min/Max-Alarm The measuring value is constantly monitored for the min and max rails. Alarming is
done by integrated horn, display and interface
Real time clock integrated clock with date and year
Logger 2 Functions: individual value logger („Stor“) and cyclic logger („Cycl)
Memory Stor: 99; Cycl: 16384
Cycletime CYCL 0:01 …60:00 (minutes/seconds, min 1s, max 1h)
Housing: impact-resistant ABS plastic housing, membrane keyboard, transparent panel.
Front side IP65, integrated pop-up clip for table top or suspended use.
Dimensions: 142 x 71 x 26 mm (L x B x D)
Weight: approx. 155 g
Directives / 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 acc. to table 3 and A.1
Additional fault: <1%
EN 50581 : 2012

H49.0.02.6C-10 User’s Guide GMH 3750 page 16 of 16
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