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2. Modes of Operation
008-0738-00
•
When in FASTMODE, the SHUNT CAL values for voltage, current and frequency are
invalid because the scaling module is bypassed, so the only piece of information that
remains valid and that we need to use from this data table is the apparent change in
TORQUE due to SHUNT CAL, and in the case of this example, it is 1692.2 Lbf.in
•
It follows that the change in analog voltage output when in FASTMODE will represent
1692.2 Lbf.in
•
The exception to this case will be when a value has been set for #SCSCALE. This
parameter allows the effect of SHUNT CAL to be varied, according to the value set.
The default is 1 and any other value acts as a multiplier – but only when the scaling
module is operating.
•
For FASTMODE operation, the scaling module is bypassed so the effect of SHUNT
CAL will be the original effect, as manufactured, and may be significantly different
from the calibration certificate value.
•
To compensate for any value of #SCSCALE, calculate as follows:
o
o
o
2.3
Analog Output Characteristics
The analog output channel is specified for a bandwidth of 3 kHz so there is no output filtering
that follows the digital-to-analog converter (DAC). This can lead to a "stair casing" effect when
the DAC is being updated at a relatively slow rate such as 1104 Hz.
For users that do not require wide bandwidth, this stair casing will not be a problem and can
be eliminated from the measurement by applying a suitable sampling rate at the data
acquisition end. Typically, a sampling rate of one quarter of the TMS 9250 DAC update rate
(or less) would be sufficient to solve this problem.
For applications where the fidelity of the output waveform is of prime importance, the solution
to stair casing is to add a filter network across the analog voltage output terminals.
When using FASTMODE, the DAC is being updated at a rate of 8828 Hz therefore stair-
casing is reduced as a result of the much faster update rate.
30
© 2012 – Honeywell International Inc. All rights reserved
Certificated change in torque due to SHUNT CAL is 1692.2 Lbf.in Value set
for #SCSCALE is 1.5
Actual change due to SHUNT CAL is 1692.2/1.5 = 1128.13 Lbf.in
If #SCSCALE is 1, then no calculation is necessary.
TMS 9250 Product User Manual
Rev B
April 2012
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