Vaisala WMT700 - Manual (Page 183)

Chapter 6 _______________________________________________________________ Maintenance
Testing Proper Operation
WMT700 measures the time it takes for an ultrasonic signal to
travel from one transducer to another. Therefore, the accuracy of
the sensor depends on the distance between the transducers and
the time-of-flight measurement circuit, which uses a crystal
oscillator for its time reference.
If necessary, you can verify the distance between the transducer
arms with an optional verifier. You can order WM Verifier from
Vaisala as an accessory; see Table 62 on page 192.
Vaisala recommends that you perform the test every 12 months or
if you suspect that the transducers may have been damaged. The
test can be performed either in the field or in a laboratory. Do not
perform the test when the wind speed is more than 10 m/s, or
when there is a risk of thunderstorm in the area.
NOTE Disable heating before performing the verifier test. You can do this either
by disconnecting the heater supply voltage or by setting the heaterOn
parameter to 0.
To perform the test:
1. Slip the verifier over the three transducers. To see how the
verifier fits over the transducers, see Figure 51 on page 182.
2. Start wind measurement. The command depends on the
selected communication profile.
3. Make sure that WMT700 reads less than 0.5 miles per hour
(0.22 m/s) with the verifier in place.
4. Remove the verifier.
NOTE Some random data samples may be lost during the verifier test. This,
however, does not indicate that WMT700 is faulty.
VAISALA _______________________________________________________________________ 181