2
Calibration
NOTE: Because the transmitter cannot output a negative current, the calibration of the zero
cannot be performed at 0 °C (0 mA). The zero calibration should be performed at 6 °C (.05 mA)
to ensure proper calibration of the transmitter. If the transmitter is calibrated at 0 °C, the output of
the transmitter may not be linear.
1.
Select the desired temperature range by soldering the two designated pins together.
For 0 to 120 °C
Solder jumper 1 to A
For 0 to 160 °C
Solder jumper 2 to A
For 0 to 180 °C
Solder jumper 3 to A
2. Connect a power supply of 24 VDC, a 1000
Ω
load resistor (decade box), and a digital
multimeter (4-½
digit minimum) as shown below. The load resistor should have an accuracy of
1000
Ω
+/- .1
Ω
. If unsure of the decade box's accuracy, measure using the DMM. Other load
resistances can be used as long as the maximum of 1000
Ω
is not exceeded. The required
calibration voltage measured on the DMM is dependent on the value of Rload according to the
following formula: V(DMM) = Rload x Current (Ohm's Law)
3. Connect a resistance decade box with a resolution of at least .01 ohms to the input of the
transmitter. If unsure or concerned about the decade box's accuracy, measure the zero and span
resistance settings using a known-accurate ohmmeter and record decade box settings before
connecting decade box to the transmitter.
4. Set decade box resistance to simulate 6 °C (102.34
Ω
).
5. Adjust ZERO potentiometer until the meter reads .05 volts (.05 volts x 1000
Ω
= .05 mA).
6. Set decade box resistance to simulate the desired span temperature.
For 120 °C
R = 146.061
Ω
For 160 °C
R = 161.043
Ω
For 180 °C
R = 168.478
Ω
7. Adjust SPAN potentiometer until the meter reads 1 volt (1 volt x 1000
Ω
= 1 mA).
8. Repeat steps 4 - 7 until no further adjustment is necessary. The zero and span pots are non-
interacting so further adjustment should be minimal.