6 | Bases for measurement
GMH 3331
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B-H77.0.01.DB2-1.0
– STS 020 measures the flow of air
When used incorrectly, the measurement result is unusable!
Observe maximum measuring ranges!
– STS 005: 0.05 .. 5.00 m/s (water)
– STS 020: 0.5 .. 20.00 m (air)
Higher speeds can destroy the measuring head or at least permanently impair the
measuring accuracy. The specified flow direction is marked with an arrow on the
measuring head.
Flow measuring probes are free-jet calibrated, i.e. the diameter of the flow channel to
be measured must be at least 5 times the diameter of the flow measuring head. Ap-
prox. 5 cm, otherwise there will be a measuring error of up to 40%!
When evaluating the measurement results, also observe that the flow speed in the
middle of a channel is higher than at the edge of the channel. There are relevant
tables for calculation of the airflow rate based on the flow speed.
6.3.1 Averaging processes for flow measurement
Significant measurement fluctuations usually occur with measurements of flows. Two
averaging processes can be integrated in order to display a stable measurement:
6.3.1.1 Continuous averaging
This displayed average is calculated from the last measurements over the time period
of the adjusted averaging time and displayed. After the device has been switched on,
the remaining time until the averaging time has expired is displayed in the lower dis-
play line. The Min and Max values are based on the smallest and largest displayed av-
erage.
6.3.1.2 Averaging at the push of a button (Average Hold)
After the product is switched on, it begins to generate the average of the flow meas-
urement for the duration of the averaging time. The current measurement appears in
the main display during the measurement and the remaining measuring time appears
in the secondary display. After the measurement is completed, the average is dis-
played and the product switches to HOLD mode. The Min and Max values are based
on the smallest and largest measurement while the average is being calculated.
The
store
button must be pressed to start a new measurement.
6.3.2 Additionally with optional Typ-K temperature probe on
T2
The temperature of the medium, for example, can be measured with temperature
channel T2. The unaveraged measurement is display.
6.4 Universal output
The output can be used as a serial interface (for USB 3100, USB 3100N, GRS 3100
or GRS 3105 interface converters). If the output is not required, it should be deactiv-
ated,
OVT OFF
. The battery consumption will be drastically reduced as a result.
