3200 Series
92 Part No HA028651 Issue 7.0 Apr-09
16.1.4
To Check RTD Input Calibration
Connect a decade box with total resistance lower than
1K and resolution to two decimal places in place of the
RTD as indicated on the connection diagram below
before the instrument is powered up
. If at any instant
the instrument was powered up without this connection
then at least 10 minutes must elapse from the time of
restoring this connection before RTD calibration check
can take place.
Figure -3: Connections for RTD Calibration
The RTD range of the instrument is -200 to 850
O
C. It is,
however, unlikely that it will be necessary to check the
instrument over this full range.
Set the resistance of the decade box to the minimum
range. For example 0
O
C = 100.00
Ω
. Check the
calibration is 0.25% of r 1LSD.
Set the resistance of the decade box to the maximum
range. For example 200
O
C = 175.86
Ω
. Check the
calibration is 0.25% of r 1LSD.
16.2
Offsets
The process value can be offset to take into account
known errors within the process. The offset can be
applied to any Input Type (mV, V, mA, thermocouple or
RTD).
A single offset can be applied - the procedure is carried
out in the
I N P U T
list and has been described in section
8.2.
It is also possible to adjust the low and high points as a
two point offset. This can only be done in
Level 3
in the
‘
C a l
’ list and is described below.
16.2.1
Two Point Offset
A two point offset adjusts both a low point and a high
point and applies a straight line between them. Any
readings above and below the calibration points will be
an extension of this straight line. For this reason it is
best to calibrate with the two points as far apart as
possible as shown in the example below:-
Figure 4 Two Point Offset Applied to Linear and Non-linear Inputs
Matched impedance copper
leads
Decade
Box
Controller
VI
V-
V+
Electrical
Input
Display
Reading
High offset
(e.g. 10.0)
Factory
calibration
Low offset
(e.g. 8.0)
Electrical
Input
Display
Reading
High offset
Factory
calibration
Low offset
