2.4 Optional Display
The transmitter is also available with an optional graphical 128*64 pixel resolution LCD display.
The display shows the measurement results of selected parameters in selected units (defined
when ordering the transmitter). The parameters are displayed simultaneously on two separate
rows on the display.
2.5 Interchangeable Probe
The HMP110 relative humidity probe used in the transmitter is fully interchangeable. You can
easily remove the probe and replace it with a new one without having to adjust the transmitter.
You have the following options when purchasing a new probe from Vaisala:
• Order a new probe and keep your current one.
• Order a new probe and return the old one to Vaisala (replacement probe).
Only probes that have a compatible digital output (VDIGI mode) can be used with
the transmitter. Compatible probes have the letter "V" as the first letter in their
order code. The order code is written on the probe.
2.6 Constant Output Probe
The constant output probe HMP110REF is a testing accessory that can be used to check
transmitter's functions and measurement signal transfer chain all the way to the control
system. The constant output probe does not measure humidity and temperature; instead, it
outputs constant humidity and temperature readings.
The values output by the constant output probe are
specified when ordering. These values are
written on an additional label on the probe body.
The procedure for using the constant output probe is simply to replace the original probe for
the duration of the testing:
1. Disconnect the normal probe from transmitter.
2. Connect the constant output probe to the transmitter.
3. Check that all used outputs (analog, display, serial line) show the correct measurement
values.
4. After checking the outputs, disconnect the constant output probe and reconnect the
original probe.
The transmitter goes to the error state for a short time when the probe is
changed. This is normal.
HMT120 User Guide M211244EN-C
10
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