Vaisala HMT120 - Manual (Page 67)

Chapter 5 _______________________________________________________________ Maintenance
VAISALA ________________________________________________________________________ 65
Analog Output Tests
HMT120 has a built-in software function for testing the analog outputs.
To test the outputs, do the following:
1. Make sure the transmitter is not in adjustment mode.
2. Press the + adjustment button (see Figure 16 on page 50).
This sets the output current level to the high point of the analog
output range (20mA nominal). The output stays at this level for
about 30 seconds after the + adjustment button has been pressed.
3. Press the - adjustment button (see Figure 16 on page 50).
This sets the output current level to the low point of the analog
output range (4mA nominal). The output stays at this level for
about 30 seconds after the - adjustment button has been pressed.
HMT120 analog output current can be measured without removing the
wires from the screw-terminals by using a low-impedance multimeter
between the associated +-terminal and test point (CH1 or CH2) on the
component board, see figure 1011-157
Figure 21 below for reference.
1011-157
Figure 21 HMT120 Output Current Measurement
NOTE In case of using a HMT120 transmitter with display option, the
following texts are shown at the display during analog output test:
"Analog output test high" corresponding to 20mA current output
"Analog output test low" corresponding to 4mA current output