Spectrum Controls 1769sc-IF8u - Manual (Page 63)

Chapter 4: Module Data, Status, and Configuration 53
If you enable the cyclic autocalibration function, the module update time
increases when the autocalibration occurs. To limit its impact on the
module update time, the autocalibration function is divided over two
module scans. The first part (offset/0) of a channel calibration adds 73 ms
and the second part (gain/span) adds 101 ms to the module update. This
takes place over two consecutive module scans. Each enabled channel
requires a separate offset/0 and gain/span cycle, unless any channel to be
scanned uses an Input Type of the same Input Class as any previously
calibrated channel. In that case, offset and gain calibration values from
the previous channel are used, and no additional time is required.
Calculating Module Update Time
To determine the module update time, add the individual channel update
times for each enabled channel and the CJC update time if any of the
channels are enabled as thermocouple inputs.
EXAMPLE 1.Two Channels Enabled for Millivolt Inputs
Channel 0: ±50 mV with 60 Hz filter
Channel 1 Input: ±50 mV with 500 Hz filter
From Table 4.7, Channel Update Time:
Module Update Time
= Ch 0 Update Time + Ch 1 Update Time
= 56 ms + 12 ms
= 68 ms
EXAMPLE 2.Three Channels Enabled for Different Inputs
Channel 0 Input: Type J Thermocouple with 10 Hz filter
Channel 1 Input: Type J Thermocouple with 60 Hz filter
Channel 2 Input: ±100 mV with 250 Hz filter
From Table 4.7, Channel Update Time:
Module Update Time
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time (uses lowest thermocouple filter
selected)
= 305 ms + 56 ms + 18 ms + 305 ms
= 684 ms
EXAMPLE 3.Three Channels Enabled for Different Inputs with
Cyclic Calibration Enabled
Channel 0 Input: Type T Thermocouple with 60 Hz Filter
Channel 1 Input: Type T Thermocouple with 60 Hz Filter
Channel 2 Input: Type J Thermocouple with 60 Hz Filter