Model TT231-0600
Two-Wire RTD Transmitter w/USB
Acromag, Inc. Tel: 248-295-0880
- 20 - http://www.acromag.com
- 20 -
http://www.acromag.com
Zero, Full-Scale, & Linearizer Calibration Procedure
By default, the unit is factory calibrated to a 100Ω, Pt385 RTD type, using a 3-wire
sensor connection, and a 0° to 200°C input span to drive a 4mA to 20mA output
span. For our example below, we will instead use the 0 to 500
C portion of the Pt
RTD type to drive a 4 to 20mA output range.
Zero, Full-Scale, & Linearizer Calibration Procedure
1. After configuring your input type and I/O ranges, you can begin calibrating the
transmitter by clicking the “Start Calibration” button and the following message
will appear:
Your unit needs to calibrate its zero signal. The software used your input type
and alpha information to compute the equivalent RTD resistance of the input
zero value you specified, and returned that value in this prompt. Click OK and
this message is repeated in the system message window at the bottom of the
screen. Adjust your input signal to the zero input value noted. Because this
input is a Pt 100Ω sensor, and 0°C is our input zero, our input signal should be
precisely set to 100.00 ohms. Measure the corresponding output current and
type the measured current in milliamps into the Measured Current Output
field. Then click the “Go To Step 2” button.
2. After clicking “Go To Step 2”, the following message will be displayed:
Now the unit needs to calibrate its gain to produce your full-scale endpoint.
The software used your input type and alpha information to compute the
equivalent RTD resistance of the input full-scale value you specified, and
returned that value in this prompt. Click OK and this message is repeated in the
system message window at the bottom of the screen. You need to adjust your
input signal to the full-scale input value noted. Measure the corresponding
output current accurately and type the measured output current in milliamps
into the Measured Current Output field. Then click the “Go To Step 3” button
(only Pt RTD inputs will require a 3
rd
step).
Note that at this point, your output signal will not be an accurate full-scale
output (RTD Input), as linearization is OFF and calibration has not been
completed. The second step only sets the gain of the PGA amplifier to drive the
full-scale output, but without RTD linearization turned on.
If your Input Type is Resistance, your calibration is complete after this step
because no special linearization correction applies (your output is already linear
with resistance). You simply need to click the Complete Calibration button to
continue and your resistance transmitter should be calibrated.