VMS-1655M
LIT-12013297
18
Figure 19: Comm port number
Make sure that the VMS sensor powers on. The USB plug flashes red for the request and green as a response from the sensor.
Some of the pressure and face velocity fields populate. The GET buttons request and present the associated information.
Get Serial,
Get Date,
and
Get FW Rev
return preset information about the sensor unit. The sensor is in an operating and calibrated condition
from the factory settings, but you can field-calibrate various aspects.
Note:
As the airflow in the fume hood is turbulent, the pressure readings that you use to compute face velocity can also be noisy. You can
dampen the pressure readings with a Filter Factor parameter. The greater the number is, the larger the damping effect on the face velocity
reading is, and also the slower the response with changes in the face velocity is. In most cases, a starting value of 4 to 6 is sufficient.
Figure 20: Filter Factor
You can calibrate the measured Face Velocity to conform with the specifics of the local fume hood. The sensor uses a two-point calibration.
The first point is the zero or offset calibration. Before calibration, you must cap the sensor to remove any air pressure from the hood on it.
To achieve the first point, zero or offset calibration, complete the following steps:
1. Cap the ¼ in. nipple exposed inside the hood with the red sensor cap.
2. In the
VMS configuration tool
, watch the
Observed Face Velocity
field and wait until the value is stable, this may or may not be 0.
3. When stable, click the
Set 0 Flow
button.
Figure 21: Observed Face Velocity