Mitsubishi Melsec FX-4AD User Manual page 9

4 DEFINING GAIN AND OFFSET
(a)
Gain
1000
Digital
Gain value
Analog
Gain determines the angle or slope of the calibration line,
identified at a digital value of 1000.
(a) Small gain -- Large steps in digital readings
(b) Zero gain --- default : 5V or 20mA
(c) Large gain - Small steps in digital readings
Offset and gain can be set independently or together. Reasonable offset ranges are -5 to +5V or -20mA to
20mA, and gain values 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-4AD (with the aid of a voltmeter/ammeter)
Bit device's b1, b2 of the gain/offset BFM #21 should be set to 0, 1 to allow adjustment.
Once adjustment is complete these bit devices 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 the system up (the FX base unit can be in either RUN or STOP mode).
2. Set the FX-4AD MODE switch to the first channel number.
3. Apply the offset analog input to the terminal of the channel.
4. Press the OFFSET button once. The digital offset value (converted from the analog input value) is
stored in the FX-4AD.
5. Apply the gain analog input to the input terminal of the channel to be adjusted.
6. Press the GAIN button once. The digital gain value is stored in the FX-4AD.
7. Repeat operations 3 to 6 for each channel you wish to use.
8. Set the FX-4AD MODE switch to READY to complete gain and offset adjustment.
NOTE: If the MODE switch is not set to a channel number, the FX-4AD is regarded as being in the READY
status and no adjustments can be made.
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(b)
Offset
(c)
Offset is the 'Position' of the calibrated line, identified at a
digital value of 0.
(d) Negative offset
(e) Zero offset - default : 0V or 4mA
( ) Positive offset
f
(d) (e) (f)
Digital
0
Offset value
Analog