WIKA T91.30 - Manual (Page 2)

230 VAC
24 VDC
Load
(PLC, PC)
Thermocouple
C_212-232.01
Zero Span
8 7 6
2 3
4.3 Electrical connection 0 ... 10 V output signal
Pt100
230 VAC
24 VDC
Load
(PLC, PC)
8 7 6
1 3 4
C_254.01
Span Zero
Model T91.30.254
Pt100 in 2- or 3-wire connection.
With a 2-wire connection, the resistance of the input leads affects
the measurement results. Therefore this connection should only
be selected if the wires are short, or accuracy requirements are
low. If using a 2-wire connection, always connect a jumper
between input terminals 3 and 4.
Model T91.30.232
The positive lead of the thermocouple is connected to terminal 3
on the transmitter and the negative lead to terminal 2.
The transmitter is galvanically isolated between input and output;
so non-isolated thermocouples can therefore be used.
4.2 Thermocouple input
Model T91.30.212
The positive lead of the thermocouple is connected to terminal 3
on the transmitter and the negative lead to terminal 2.
The output voltage follows the applied input voltage linearly.
There should be no galvanic coupling between the sensor and the
supply or output voltage.
5.1 Preparation
Connect a suitable simulation source to the input of the T91
(Pt100 or thermocouple simulator). When simulating a Pt100,
connect the simulator in a 2-, 3- or 4-wire configuration.
We recommend the use of passive resistances.
When simulating a thermocouple, the actual terminal temperature
of the transmitter must be pre-set on the simulator (Cold Junction
Compensation).
T Connect a multimeter to the 0 … 10 V output signal
T Connect a suitable power supply to the transmitter
5.2 Adjustment
1) Set the simulator with approx. 1 V offset from the lower limit of
the measuring range. (e.g. -20 °C = 1 V for a measurement
range -30 ... +70 °C)
2) Turn the zero potentiometer Z, until the output signal (in our
example -20 °C = 1 V output signal) matches the desired value
3) Set the simulator to the upper limit of the measuring range ,
e.g. +70 °C for measurement range -30 ... +70 °C
4) Turn the span potentiometer S, until the output signal (in our
example 70 °C = 10 V) matches the desired value
5) Repeat step 1 and check signal (1 V)
6) Repeat step 3 and check signal (10 V)
5.3 Closing steps
Disconnect the simulator, the multimeter and the power supply
6. Fault diagnostics
When measuring with resistance thermometers or thermocouples,
factors arising from the design and measuring technology used
can falsify the results measured. The most important effects that
can lead to faults are listed below:
Error Possible cause
No voltage output - No supply voltage
- Display unit not working
- Circuit interruption in the supply line
Output signal
1) 0 V
- Short circuit in the Pt100
2) corresponds to room temperature - Short circuit in the thermocouple
Output signal - Sensor break
> 10 V
Temperature read out
- Poor lead insulation resistance
too low/fluctuates
Read out obviously
- Moisture in the sensor or in the senor
too high or too low wire
- Not correct compensation wire or
incorrect thermocouple
If the measuring point is - Thermocouple polarity incorrect
heated up the output signal
reduces
When only one pole of the
- Electromagnetic disturbances are
thermocouple is connected, coupled to the input lead
a value is still displayed - Through poor galvanic isolation, and
poor insulation, parasitic voltages are
present, e.g. through the thermal
insulation
Displayed value obviously - Electromagnetic disturbances are
incorrect coupled to the input lead
- Parasitic galvanic voltages, e.g. as a
result of moisture in the compensation
cable insulation
5. Transmitter adjustment
Zero point and Span adjustment is carried out via potentiometers.
These are under the transparent cover. To open the transparent
cover, it must be pressed inwards on its shortest sides and pulled
away carefully. The potentiometers are protected against
accidental alteration.
The zero-point potentiometer can be adjusted to make small
corrections. After any adjustment of the span potentiometer, a
complete adjustment of the transmitter is necessary.
Maximum power supply: 15 …35 VDC (reverse-polarity protected)
The output voltage follows the applied input signal linearly.
Please note that the output can only be regulated to within
approx. 0.02 V at the lower supply voltage.
Model Terminals
T91.30 6 (+signal), 8 (+24 V), 7 (-GND)