Metasys TC-9100 Series - Page 11

Technical Bulletin—TC-9100 Universal Controller 11
Item Tag
(Cont.)
Type Description
LRIn Number
Low Range for AIn: value represented by the lowest input
signal (0 or 2 VDC). This value must be 0 for an input with
the square root option. Use OFSn for zero offset correction.
The analog value is calculated as follows:
Linear:
AI = (PI% + OFS) / 100 x (HRI - LRI) + LRI
Square Root (LRI = 0):
(
)
AI (PI% + OFS) 100 HRI=×
where:
AI = Analog value
PI% = Analog input in % of the physical input range
(10 VDC, or 8 VDC for 2 to 10 V linear)
OFS = Offset Value
OFSn Number
Offset Value for AIn: value added to the analog input in %
of the physical input range. This parameter is normally
used to offset an input to the square root range from a
differential pressure transducer, for example, where the
output of the transducer is not at “true zero” (0 or 2 VDC)
when the physical differential pressure is zero. (See LRIn
for analog value calculation using OFSn.)
FTCn Number
Filter Time Constant: (in seconds) to reduce cyclic
instability or rapid changes in the analog input. The effect
of the filter is as follows:
AI
t
= AI
t-1
+ [1 / (1 + FTC)] x (AI - AI
t-1
)
where:
AI
t
= Filtered analog value at current time
AI
t-1
= Filtered analog value at previous poll
AI = Actual analog value at current time
If FTC = 0:
AI
t
= AI
HIAn Number
High Alarm Value for AIn: if no high limit is required, enter
a number greater than HRIn.
LOAn Number
Low Alarm Value for AIn: if no low limit is required, enter
a number lower than LRIn.
If an analog input is configured but not connected to a sensor, install a
wire jumper between the input terminal and the analog common terminal
to keep the analog input at its low range value.