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(4) Status Information BFM #29
Bit devices of BFM #29
b0 : Error
b1 : Offset / gain error
b2 : Power source abnormality
b3 : Hardware error
b10 : Digital range error
b11: Averaging error
b12: Offset / gain adjust prohibit Prohibit-(b1, b0) of BFM #21 is set to (1, 0) Permit-(b1, b0) of BFM #21 is set to (0,1)
NOTE: b4 to b7, b9 and b13 to b15 are undefined.
(5) Identification Code BFM #30
The identification (or ID) code number for a Special Function Block is read using the FROM command.
This number for the FX
2N
The user's program in the PC can use this facility in the program to identify the special function block before
commencing data transfer from and to the special function block.
CAUTION
•
Values of BFM #0, #23 and #24 are copied to EEPROM memory of the FX
are only copied when data is written to the gain/offset command buffer BFM #22. Also, BFM #20 causes
writing to the EEPROM memory. The EEPROM has a life of about 10,000 cycles (changes), so do not
use programs which frequently change these BFMs.
•
Because of the time needed to write to the EEPROM memory, a delay of 300 ms is required between
instructions that cause a write to the EEPROM.
Therefore, a delay timer should be used before writing to the EEPROM a second time.
4
Gain
+1,000
Digital
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
program example 2)
•
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.
When any of b1 to b4 is ON.
If any of b2 to b4 is ON, A/D conversion of
all the channels is stopped
Offset/Gain data in EEPROM is corrupted
or adjustment error.
24V DC power supply failure
A/D converter or other hardware failure
Digital output value is less than -2048 or
more than +2047
Number of averaging samples is 4097 or
more or 0 or less (default of 8 will be used)
-4AD unit is K2010.
DEFINING GAIN AND OFFSET
(a)
(b)
(c)
Gain value
Analog
ON
Offset
Digital
0
Offset is the 'Position' of the calibrated line, identified at a
digital value of 0.
(d) Negative offset
(e) Zero offset
(f)
Positive offset
OFF
No error
Offset/Gain data normal
Power supply normal
Hardware Normal
Digital output value is normal.
Averaging is normal.
(between 1 and 4096)
-4AD. BFM #21 and BFM #22
2N
(d)
(e)
Offset value
Analog
default : 0V or 4mA
main unit (see
2N
(f)
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