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4
DEFINING GAIN AND OFFSET
〈 〈 〈 〈 〈 GAIN〉 〉 〉 〉 〉
(a)
Analog
Gain value
1000
Digital
Gain is the angle or slope of the calibration line
identified at a digital value of 1000.
(a) Large gain – low reading resolution
(b) Zero gain - – default 5V or 20mA
(c) Small gain – high reading resolution
Offset and gain can be used independently or together. Reasonable offset ranges are -5V to +5V or
-20mA to 20mA, and gain-offset difference 1V to 15V or 4mA to 32mA. Gain and offset can be adjusted by
software in the FX base unit (see program example 2) or by the switches on the FX-2DA (with the aid of a
voltmeter/ammeter).
Bit device's b0, b1 of the gain/offset BFM (#21) should be set to 0, 1 to allow adjustment.
Once adjustment is complete these bit device should be set to 1, 0 to prohibit any further changes.
Channel initialization (BFM #0) should be set to the nearest range, i. e. voltage/current etc.
1. Power up the system the FX base unit can be in either RUN or STOP mode.
2. Connect the load and voltmeter or ammeter to the CH1 terminals.
3. Set the FX-2DA MODE switch to output CH1.
4. Press the OFFSET button once. The offset value is output. Use the UP/DOWN switch to reach the desired
offset value.
5. Press the GAIN button once. The gain value is output. Use the UP/DOWN switch to reach the desired
offset value.
6. Repeat operations 3 to 5 for each channel you wish to use.
7. Set the FX-2DA MODE switch to READY to complete gain and offset adjustment.
NOTE : If the MODE switch is not set to a channel number, the FX-2DA is regarded as being in the
READY status and no adjustments can be made.
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〈 〈 〈 〈 〈 OFFSET〉 〉 〉 〉 〉
(b)
Analog
Digital value 0
(c)
Offset is the 'Potion' of the calibrated line, identified
at a digital value of 0.
(d) Positive offset
(e) Zero offset – default (4-20mA default is 4mA)
( ) Negative offset
f
(d)
(e)
(f)
Digital
Offset value
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