User`s guide

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

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 tes

t. This,

however, does not indicate that WMT700 is faulty.

VAISALA _______________________________________________________________________ 181