Sensor Technology RWT420, Руководство пользователя

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Sensor Technology 2016
Page 14
RWT3745V (Rev 2)
Zeroing the transducer
Zeroing the transducer has the effect of introducing an offset to the torque reading. The zero
can be used to remove any offset that may have been introduced from its mechanical
installation or from idle torque present. It must be stressed that the zero offset is no substitute
for correct installation.
When using high zero offsets, care must be taken not to overstrain the transducer. A zero
offset will not extend the full scale rating of the transducer, e.g. if a transducer was zeroed at
50% then a further 50% was applied, the transducer will have reached full scale, even though
the transducer would be reading of 50%. A zero offset of 10% or greater will trigger a warning
condition and will be indicated by a warning LED sequence.
The transducer can be zeroed by using either a digital command or an electrical signal.
There are 3 zero modes that can be used:
▪
Normal Zero: Sets the zero offset to the current torque reading.
▪
Average Zero: Sets the zero offset to the average of 8 consecutive torque readings.
▪
Fixed Zero: A fixed value can be input and saved. Fixed Zero is only available in
Transducer Control.
Unless the zero is saved, any zero offset applied will be lost after a power cycle.
Electrical Signal
Zeroing the transducer electrically can be achieved by grounding the Zero Input on pin 7 of
the Analog 15 Way ‘D’ Socket. The best way of zeroing a transducer is to use a push button.
A simple circuit diagram using a push button is shown below.
The zero action is only carried out once the input has been ungrounded. Grounding the zero
input momentarily (less than 2 seconds) will initiate a normal zero, grounding the input for
longer will initiate other modes. When the zero input is grounded for more than 2 seconds the
LED will start flashing to indicate that a new mode has been selected, subsequent mode
changes are shown by an increase in flash frequency. The LED will not flash if an error
condition is present.
The table below shows the various modes and timings.
Ground Hold Time LED Flash Zero Mode / Action
0 - 2 Seconds None Normal Zero
4 - 6 Seconds 1 Hz Green Flash Average Zero
Greater than
6 Seconds 2 Hz Green Flash
Transducer will save the current zero
offset so that it is remembered across
power cycles.