LX3V-4TC
5
WECON Technology CO., LTD.
BFMs #21 to #27 and #31 are reserved. All non-reserved BFMs can be read by the PLC using the
FROM instruction.
BFMs (buffer memories) marked with an “*” can be written to, the special function block using
the TO instruction.
1)
Buffer Memory BFM #0: Thermocouple Type K or J selection mode
BFM #0 is used to select Type K or J thermocouples for each channel. Each digit of a 4 digit
hexadecimal number corresponds to one channel, the least significant digit being channel 1.
Example
A/D conversion time is 240ms per channel. When “3" (unused) is set for a channel, A/D
conversion is not executed for that channel, therefore, the total conversion time is
decreased. In the above example, the conversion time is as follows:
240ms (conversion time per channel) × 2channels (number of channels used) = 480ms
(total conversion time)
2)
Buffer Memory BFMs #1 to #4: Number of temperature readings to be averaged
When the number of temperature readings to be averaged is specified for BFMs #1 to #4, the
averaged data is stored in BFMs #5 to #8 (°C) and #13 to #16 (°F). Only the range 1 to 256 is
valid for the number of temperature readings to be averaged. If a value outside of this range is
entered, a default value of 8 is used.
3)
Buffer Memory BFMs #9 to #12 and #17 to #20: Present temperature
These BFMs store the present value of the input data. This value is stored in units of 0.1°C or
0.1°F, but the resolution is only 0.4°C or 0.72°F for Type K and 0.3°C or 0.54°F for Type J.
4.5
States information
1)
Buffer memory BFM#28: Digital range error latch
BFM #29 b10 (digital range error) is used to judge whether the measured temperature is within
the unit’s range or not.
BFM #28 latches the error status of each channel and can be used to check for thermocouple
0= Type K
1= Type J
3= Not used
