GSG GMH 3750 User manual

H49.0.02.6C-04
Operating Manual Precision Thermometer
GMH 3750
from Version 1.0
For Pt100 4-Wire Temperature Probes

H49.0.02.6C-04 Operating Manual GMH 3750 Page 2
Index
1 IN GENERAL.............................................................................................................................................................................2
1.1 SAFETY INSTRUCTIONS .........................................................................................................................................................2
1.2 OPERATING AND MAINTENANCE ..........................................................................................................................................3
1.3 CONNECTIONS.......................................................................................................................................................................3
1.4 DISPLAY ELEMENTS ..............................................................................................................................................................3
1.5 PUSHBUTTONS ......................................................................................................................................................................3
2 DEVICE CONFIGURATION...................................................................................................................................................4
3 SOME BASICS OF PRECISION TEMPERATURE MEASURING....................................................................................5
4 SPECIAL FUNCTIONS ............................................................................................................................................................6
4.1 DISPLAY RESOLUTION...........................................................................................................................................................6
4.2 USER SENSOR CURVE ('LIN USER') ......................................................................................................................................6
4.3 ZERO DISPLACEMENT ('OFFSET')...........................................................................................................................................6
4.4 SCALE CORRECTION ('SCALE') ..............................................................................................................................................6
4.5 OUTPUT.................................................................................................................................................................................6
4.5.1 Interface - Base Address ('Adr.') ..................................................................................................................................6
4.5.2 Analogue Output – Scaling with DAC.0 and DAC.1....................................................................................................7
4.6 ALARM..................................................................................................................................................................................7
4.7 REAL TIME CLOCK ................................................................................................................................................................7
5 OPERATION OF LOGGER.....................................................................................................................................................8
5.1 „FUNC-STOR“: STORING SINGLE MEASUREMENTS................................................................................................................8
5.2 „FUNC-CYCL“: AUTOMATIC RECORDING WITH SELECTABLE LOGGER-CYCLE-TIME ..........................................................9
6 FAULT AND SYSTEM MESSAGES.....................................................................................................................................10
7 PROBE PIN ASSIGNMENT ..................................................................................................................................................10
8 CALIBRATION SERVICES ..................................................................................................................................................10
9 TECHNICAL DATA ...............................................................................................................................................................11
10 DISPOSAL NOTES ................................................................................................................................................................11
1 In General
1.1 Safety Instructions
This device has been designed and tested in accordance to 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 it.
1. Trouble-free operation and reliability of the device can only be guaranteed if it is not subjected to any other climatic conditions than those
stated under “Specification”.
2. Transporting the device from a cold to a warm environment condensation may result 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.
3. The circuitry has to be designed most carefully if the device should be connected to other devices. Internal connection in third party devices
(e.g. connection GND and earth) may result in not-permissible voltages impairing or destroying the device or another device connected.
4. Warning: Operating the device with a defective mains power supply (e.g. short circuit from mains voltage to output voltage) may result in
hazardous voltages at the device (e.g. at sensor socket)
5. Whenever there may be 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.
6. Warning: Do not use these product as safety or emergency stop device, 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.

H49.0.02.6C-04 Operating Manual GMH 3750 Page 3
1.2 Operating And Maintenance
•Battery Operation
The battery has been used up and needs to be replaced, if and „bAt“ are shown in lower display.
The device will, however, continue operating correctly for a certain time.
The battery has been completely used up, if ´bAt´ is shown in the upper display.
The battery has to be taken out, when storing device above 50°C.
Hint: We recommend to remove the battery if device is not used for a longer period of time!
•Mains Operation
Attention: When using a power supply unit please note that operating voltage has to be 10.5 to 12 V DC. Do not
apply overvoltage!! Simple 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 plug power supply with the mains supply make sure that the operating voltage stated at the
power supply is identical to the mains voltage.
•Treat device and probes carefully. Use only in accordance with above specification. (do not throw, hit against etc.).
Protect plugs and sockets from soiling.
•To disconnect 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.
1.3 Connections
1. Output: Operation as interface: Connect to optically isolated
interface adapter (accessory: GRS 3100 or GRS3105)
Operation as analogue output: Connection via suitable cable.
Attention: The output mode has to be configured (p.r.t. 2.7) and
influences battery life!
2. Probe connection Pt100 4-wire
3. The mains socket is located at the left side of the instrument
1.4 Display Elements
1 = Main Display: Currently measured temperature
2 = Auxiliary
Display:
Display of min, max or hold values
Special display elements:
3 = Warning
triangle:
indicates a low battery
4 = Corr-arrow:indicates that correction factor is activated
5 = Offset-arrow:indicates that zero point offset (offset) is activated
6 = Min/Max/Hold:shows if a min., max. or hold value is displayed in
the secondary display
7 = Alarm-arrow:Flashes if alarm is present
8 = Logg-arrow:Shown if logger function is selected,
flashes if cyclic logger is running
1.5 Pushbuttons
key 1: On/Off key
key 4: Set/Menu
press (Menu) for 2 sec.: configuration will activated
keys 2, 5: min/max when taking measurements:
press shortly: min. or max. measuring value will be displayed
press for 2 sec.: the min. or max. value will be deleted
up/down for configuration:
to enter values or change settings
key 6: Store/Quit
- Measurement: Hold current measuring value ('HLD' in display) or
operation of logger functions (p.r.t. Chapter 5)
- Menu: Acknowledge setting, return to measuring
key 3: When taking measurements: no function
During configuration: Selection of menu-parameter
!

H49.0.02.6C-04 Operating Manual GMH 3750 Page 4
2 Device Configuration
Note: Some menu items will be shown depending on the actual device configuration (e.g. there are some
items disabled when the logger contains data). Please note the hints by the menu items.
For configuration of the device press "Menu"-key (key 4) for 2 seconds, the main menu will be shown (main display:
“SEt”). Choose the desired menu branch by pressing the "Menu"-key (key 4). By pressing “4” (key 3) the referring
parameters can be chosen. The referring values are changed by pressing the keys "5" (key 2) or "6" (key 5) (Choice
of parameter: “4”). Pressing “Menu” (key 4) again will jump back to the main menu selection and stores the settings.
Use key "Quit" (key 6) to leave configuration.
Menu Parameter Values Meaning
key Menu key4key5or 6p.r.t.
Set Configuration: Generic Settings
°C: All temperature values are in degrees Celsius
°F: All temperature values are in degrees Fahrenheit
*
0.1°: Resolution 0.1°C
0.01°: Resolution 0.01°C
Auto: Resolution is selected automatically
*4.1
E.751 Measuring / sensor curve according to EN60751
USEr User sensor curve (Predefined to EN60751 values, changeable by
software GMHKonfig)
*4.2
-2.50°C..2.50°C resp.
-4.50°F...4.50°F
The zero point of the measurement will be displaced by this value to
compensate for deviations in the probe or in the measuring device.
oFF: Zero displacement inactive (=0.0°)
*4.3
-2.000...2.000: The scale of the measuring will be changed by this factor (in %) to
compensate deviations of temperature probe or measuring device
oFF: Scale correction factor inactive (=0.000)
*4.4
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 Power-off function inactive (continuous operation, e.g. mains operation)
oFF: Function of the output: No output function, lowest power consumption
SEr: Output is serial interface
dAC: Output is analogue output 0...1V
4.5
01,11..91 Base Address when Output = Serial Interface :
Base address of device for interface communication. 4.5.1
-200.0...850.0°C resp.
-328.0...1562.0°F
Enter desired temperature value at which the analogue output potential
should be 0V 4.5.2
-200.0...850.0°C resp.
-328.0...1562.0°F
Enter desired temperature value at which the analogue output potential
should be 1V 4.5.2
Set Alarm: Settin
g
s Of Alarm Function
on Alarm on, with horn-sound
no.So Alarm on, without horn-sound
oFF no alarm function
min range
...AL.Hi
Min alarm rail (not when AL. oFF)
AL.Lo
...max range
Max alarm rail (not when AL. oFF)
4.6
Set Logger: Configuration Of Logger Function *
CYCL Cyclic: logger function ‚cyclic logger‘
Stor Store: logger function ‚individual value logger‘
oFF no logger function
*5
0:01..60:00 Cycle time of cyclic logger [minutes:seconds] *5.2
Set Clock: Setting Of Real Time Clock
HH:MM Clock: Setting of time hours:minutes
YYYY Year
TT.MM Date: day.month
4.7
Hint: The settings will be set to the settings ex works, if keys ‘Set‘ and ‘Store‘ are pressed simultaneously
for more than 2 seconds.
(*) If the logger memory contains data already, the menus/parameters marked with (*) can not be invoked!
If these should be altered the logger memory has to be cleared before!

H49.0.02.6C-04 Operating Manual GMH 3750 Page 5
3 Some 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|)
1/3 B (=1/3 DIN) ± (0,1 + 0,0017 |temperature|)
1/10 B (=1/10 DIN) ± (0,03 + 0,0005 • |temperature|)
A ± (0,15 + 0,002 • |temperature|)
error of device and probe
0
1
2
3
4
-200 0 200 400 600 800
T [°C]
error [°C]
B
1/3B
1/10B
A
GMH37xx
error of device and probe
0
0,2
0,4
0,6
0,8
1
1,2
-50 0 50 100 150
T [°C]
error [°C]
B
1/3B
1/10B
A
GMH37xx
Error over measuring range Pt100 Error over range –50...150°C Pt100
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. (For pin assignment please refer to chapter 7)
•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 cold due to the evaporation causes too low
measurings.

H49.0.02.6C-04 Operating Manual GMH 3750 Page 6
4 Special Functions
4.1 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
recording. In such a case please select the optimum resolution manually.
4.2 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. Temperature measurements with an user sensor curve beyond
the checked temperature range can possibly lead to tremendous errors. Therefore the sensor curve due to DIN EN
60751 (display: Lin E.751) has to be used for temperature measurements beyond the checked temperature range.
4.3 Zero Displacement ('Offset')
A zero displacement can be carried out for the measured temperature:
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.
4.4 Scale Correction ('Scale')
The scale of the measuring can be influenced by this setting (factor is in %):
displayed temperature[°C] = measured temperature[°C] * (1+Scal/100)
respectively displayed temperature[°F] = (measured temperature [°F]-32°F) * (1+Scal/100) + 32°F
Standard setting: 'off' =0.000, i.e. temperature is nor corrected. Together with the zero displacement (see above) this
factor is mainly used to compensate for sensor deviations.
Unless the factor is set to 'off', the Corr arrow in the display shows an active scale correction.
4.5 Output
The output can be used as serial interface (for GRS3100 or GRS3105 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.
4.5.1 Interface - Base Address ('Adr.')
By using an electrically isolated interface converter GRS3100 or GRS3105 (accessory) the device can be connected to
a PC. With the GRS3105 it is possible to connect up to 5 instruments to a single interface (please also refer to
GRS3105-manual). As a precondition the base addresses of all devices must not be identical. In case several devices
will be connected via one interface make sure to configure the base addresses accordingly. In order to avoid
transmission errors, there are several security checks implemented (e.g. CRC).
The following standard software packages are available for data transfer:
!EBS9M: 9-channel software to record and display the measuring values
!EASYControl: Universal multi-channel software (EASYBUS-, RS485-, and/or GMH3000- operation possible)
for real-time recording and presentation of measuring data in the ACCESS®-data base format.
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 Basic 6.0™, Delphi 1.0™, Testpoint™, Labview™
Note: The measuring and range values read via interface are always in the selected display
unit (°C/°F)!

H49.0.02.6C-04 Operating Manual GMH 3750 Page 7
Supported interface functions:
Code Name/Function Code Name/Function
0 read nominal value 200 read min. display range
3 read system status 201 read max. display range
6 read min. value 202 read unit of display
7 read max. value 204 read decimal point of display
12 read ID-no. 208 read channel count
22 read min. alarm rail (AL. - AL.Lo) 214 read scale correction
23 read max. alarm rail (AL. - AL.Hi) 215 set scale correction
216 read zero displacement
217 set zero displacement32
read configuration flag
alarm function: 1; Alarm horn:3;
BitLoggerOn:50; BitCyclicLogger:51; 224 Logger: read data cyclic logger
102 set min. alarm rail (AL. - AL.Lo) 225 Logger: read cycle time (LoGG - CYCL)
103 set max. alarm rail (AL. - AL.Hi) 226 Logger: set cycle time (LoGG - CYCL)
160 set configuration flag (see 32) 227 Logger: start recording
174 delete min. value 228 Logger: read #of data
175 delete max. value 229 Logger: read status
176 read min measuring range 231 Logger: read stop time
177 read max measuring range 233 read Real time clock (CLOC)
178 read measuring range unit 234 set Real time clock (CLOC)
179 read measuring range decimal point 236 Read logger memory size
180 read measuring type 240 Reset
194 set display unit 254 read program identification
199 read meas. type in display 260 Logger: read data manual logger
4.5.2 Analogue Output – Scaling with DAC.0 and DAC.1
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.
GND
plug wiring::
+Uout
Attention!
The 3rd contact has to be left floating!
Only stereo plugs are allowed!
4.6 Alarm
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 interface message.
4.7 Real Time Clock
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.

H49.0.02.6C-04 Operating Manual GMH 3750 Page 8
5 Operation Of Logger
The device supports two different logger functions:
„Func-Stor“: each time when „store“ (key 6) is pressed a measurement will be recorded.
„Func-CYCL“: measurements will automatically be recorded at each interval, which was set in the logger menu
‚CYCL‘ until the logger will be stopped or the logger memory is full. The recording is started by
pressing „Store“ 2 seconds.
The logger records 1 measurement result each time
For the 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.
5.1 „Func-Stor“: Storing Single Measurements
Each time when „store“ (key 6) is pressed a measurement and its time stamp will be recorded.
The recorded data can be viewed either in the display (when calling the configuration an additional menu „REAd LoGG“
is displayed, see below) or by means of the interface and a PC with GSOFT3050-software.
Max. number of measurings: 99
A measuring contains: - current measuring value at the time of recording
- time and date of the recording
After each recording „St. XX“ will be displayed for a short time. XX represents the number of the recording.
When logger memory contains recordings already:
When „Store“ is pressed for 2 seconds, the choice for clearing the logger memory will be displayed:
The selection can be made by 5(key 2) and 6(key 5). "Quit" (key 6) enters the choice.
If the logger memory is full, the display will show:
Viewing Recorded Measurings
Within the „LoGG Stor“ function the measurings can be viewed directly in the display not only by means of a computer
(like at „Func CYCL“): press 2 seconds „Set“ (key 4): The first menu displayed now is „rEAd LoGG“ (read logger data).
After pressing 4(key 3) the measurement recorded last will be displayed, changing between the different data
referring to the measurement also is done by pressing 4.
Changing the measurement is done by pressing the keys 5or 6.
Clear all
recordings
Clear the last
recording
Clear nothing
(cancel menu)

H49.0.02.6C-04 Operating Manual GMH 3750 Page 9
5.2 „Func-CYCL“: Automatic Recording With Selectable Logger-Cycle-Time
The Logger-Cycle-Time is selectable (p.r.t. Configuration). For example „CYCL“ = 1:00: A measuring is recorded after
each 60 seconds.
Max. number of measurings: 16384
Cycle time: 0:01...60:00 (minutes:seconds, min 1s, max 1h), selectable in the configuration
A measuring contains: - current measuring value at the time of recording
Starting a recording:
By pressing "Store" (key 6) for 2 seconds the recording will be initiated. After that the display shows ‘St.XXXXX‘ for a
short time whenever a measuring is recorded. XXXXX is the number of the measuring 1..16384.
If the logger memory is full, the display will show:
The recording automatically will be stopped.
Stopping the recording manually:
By pressing "Store" (key 6) the recording can be stopped manually. Then the following choice appears:
The selection can be made by 5(key 2) and 6(key 5). "Quit" (key 6) enters the choice.
Note: If you try to switch off the instrument in the cyclic recording operation You will be
asked once again 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!
Clear Recordings:
When „Store“ is pressed for 2 seconds, the choice for clearing the logger memory will be displayed:
The selection can be made by 5(key 2) and 6(key 5). "Quit" (key 6) enters the choice.
Stop the
recording
Do not stop the
recording
Clear all
recordings
Clear nothing
(cancel menu)

H49.0.02.6C-04 Operating Manual GMH 3750 Page 10
6 Fault 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 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
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
No display
or
weird display
Device does not
react on keypress 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
Value exceeding measuring range Check: Is the value exceeding the measuring
range specified? ->temperature too high!
Wrong probe connected Check probe
Err.1
sensor/cable defective -> replace
Value below display range Check: Is the value below the measuring
range specified? -> temperature too low!
Wrong probe connected Check probe
Err.2
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
7 Probe pin assignment
The device is constructed for the connection of a Pt100 4-wire probe. The connection is be carried out as follows:
figure shows view 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
resistance a increased measuring fault will occur.
The connection of this probes should be carried out as follows:
3-wire connection 2- wire connection
8 Calibration Services
Calibration certificates can be issued by the factory. For this the device has to be sent to the manufacturer. Just the
manufacturer can check the factory settings and correct them if necessary.
Pt100
Pt100 Pt100

H49.0.02.6C-04 Operating Manual GMH 3750 Page 11
9 Technical Data
Supported probes Pt100 4-wire (2-wire possible)
Sensor Curve according to EN60751
or with user-sensor curve (table of 50 rows and 2 columns: Ohm/°C]
Probe connection 4pole Mini-DIN socket
Resolution 0.01°C respectively 0.1°C, 0.01°F respectively 0.1°F
Measuring Ranges 0.01°C 0.1°C 0.01°F 0.1°F
–199.99... +199.99°C -200.0... +850.0°C -199.99... +199.99°F -328.0... +1562.0°F
Precision Device without probe ±1Digit (at nominal temperature)
Range 0.01°C/F Range 0.1°C/F
±0.03°C / 0.06°F ±0.1°C / ±0.2°F
Measuring 4-wire measuring with automatic compensation of thermovoltage errors,
measuring current ca. 0.3mA
Temperature drift <=0,002K per 1K for Pt100 4-wire
Nominal temperature 25°C
Ambient Temperature -25 ... +50°C (-13 .. 122°F)
rel. humidity 0 ... 95%r.F. (not condensing)
Storage temperature -25 ... +70°C (-13 ... 158°F)
Housing Dimensions: 142 x 71 x 26 mm (L x W x D)
impact-resistant ABS plastic housing, membrane keyboard, transparent panel. Front side IP65,integrated
pop-up clip for table top or suspended use.
Weight approx. 155 g
Output: 3.5mm audio plug, stereo
Selectable as serial interface: via optically isolated interface adapter GRS3100 or GRS3105 (p.r.t. accessories) directly
connectable to RS232-interfaces.
or analogue output: 0..1V, freely scaleable (resolution 13bit, accuracy 0.05% at nominal temperature, cap. load <1nF)
Min/Max-Alarm: The measuring value is constantly monitored for the min and max rails set. Alarming is done by integrated
horn, display and interface
Real time clock: Integrated clock with date and year
Logger: 2 Functions: individual value logger („Func–Stor“) and cyclic logger („Func–CYCL“)
Memory: Stor: 99 data sets; CYCL: 16384 data sets
Cycle time CYCL: 0:01...60:00 (minutes:seconds, min 1s, max 1h)
Power Supply 9V-Battery, type IEC 6F22 (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 ca. 0.90mA
output serial interface: ca. 1.15mA
analogue output: ca. 1.25mA
Display Two 4 ½ digits LCD’s (12.4mm high and 7 mm high) for temperature, min./ max values, hold function, etc.
as well as additional pointing arrows.
Pushbuttons 6 membrane keys for on/off switch, menu operation, min. and max. value memory, hold-function etc.
Min-/Max-Value Memory Both the max. and the min. value will be memorised.
Hold Function Press button to store current value.
Automatic-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 1 and 120 min.; it can be
completely deactivated.
EMC: The GMH3750 corresponds to the essential protection ratings established in the Regulations of the Council
for the Approximation of Legislation for the member countries regarding electromagnetic compatibility
(2004/108/EG)
EN61326 +A1 +A2 (Appendix B, class B), additional error: < 1% FS.
10 Disposal notes
This device must not be disposed as ‘residual waste’.
To dispose this device, please send it directly to us (adequately stamped). We will dispose it appropriately and
environmentally friendly.

H49.0.02.6C-04 Operating Manual GMH 3750 Page 12