The following procedure describes a temperature (T) measurement calibration and adjustment using serial line commands. You can use the procedure to do a one-point calibration (offset) or a two-point calibration (offset and gain). For two-point calibration, the second reference point must be at least 20 °C warmer than the first.
- Disconnect the cable from connector I of the DMT132 (if connected).
- Connect the USB cable to connector II on the DMT132, and to a USB port on your PC.
Start a terminal application and set the service port connection settings (19200 8 N 1).
Remember to check which COM port the USB cable is using.
Verify that the connection works by giving the ? command:
>?If the transmitter does not respond with device information:
- Check your serial line settings and cable connections.
- Reconnect the USB cable, restart the terminal application, and try again.
When your serial connection is working, use the L command to see the current user adjustment parameters.
Write down the T offset and gain values so you can restore them manually using the LI command, if necessary.
Use the ERRS command to see that no errors are active:
- Insert the transmitter in the temperature reference.
Give the CT command.
The output from the command shows the currently measured T value, and prompts you to enter the value of the first reference (Ref1). This is the reference on the colder end, which produces the offset correction for the measurement.
>ct T 21.0947 Ref1 ?
Wait for 20 ... 40 minutes for the reading to stabilize. Press ENTER without typing anything to update the value shown by the CT command.
T 22.1298 Ref1 ? T 22.1317 Ref1 ? T 22.1576 Ref1 ?
When the measurement shown by CT is stable, you can either apply the correction or exit the procedure:
- To apply the correction, press ENTER one last time to update the value, type the temperature of the reference in degrees Celcius, and press ENTER.
- To exit the CT command without adjusting the measurement, press the ESC key and exit this procedure.
If you only want to perform a one-point calibration (offset correction), press the ESC key after entering the correction.
The CT command will exit, and you can move to 14.
>ct T 22.1601 Ref1 ? 22 Press any key when ready
To continue with the calibration of the warmer end (gain correction), press ENTER.
Insert the transmitter in the second temperature reference and wait for 20 ... 40 minutes for the reading to stabilize.
The measurement reading for the second point will appear when the measured temperature is at least 20 °C warmer than the first reference point.
Type the temperature of the second reference point and press ENTER to apply the correction.
T 44.9847 Ref2 ? 45 OK Saving settings...done >
The CT command is now finished and both adjustments have been applied.
Use the L command to verify that the new user adjustment parameters are in use:
Use the SEND command to verify that the measurement is OK:
>send Tdf= -1.25'C >