22
8
CALIBRATION
Note. Electrical calibration is carried out prior to despatch and further calibration is not normally necessary. However, if
inaccurate or inconsistent readings are obtained, follow the procedures detailed in this Section.
8.1
Equipment Required
a) Millivolt source (cell input simulator), –20.0 to 180.0mV.
b) Millivolt source (temperature input simulator), 10.0 to 40.0mV.
c) Digital voltmeter (current output), 0 to 20mA.
d) 'Mercury-in-glass' Thermometer, to measure ambient temperature.
8.2
Preparation
a) Switch off the mains supply. Disconnect the probe and retransmission output terminations from the instrument – see Fig. 4.2.
b) Connect the millivolt sources and the milliammeter to the appropriate terminals – see Fig. 8.1.
c) With all covers fitted, switch on the mains supply to the instrument and allow ten minutes for the circuits to stabilize.
d) Select the
Electrical Calibration Page
and proceed as detailed in Section 8.3, following.
N/C
N/O N/C
N/O
E
MAINS
Power
Supply
(110V or
240V a.c.)
Retransmission
Output Monitor
(Digital Voltmeter, set to
read milliamps)
Cell Input
Simulator
(–20.0 to 180.0mV
Source)
RELAY
1
RELAY
2
RTX
HEATER
DRIVE
CELL
T/C
N L
C
C
+
H H E
+ –
SCR
–
+ –
mA
88.8
mV
88.8
mV
88.8
Temperature
Input Simulator
(10.0 to 40.0mV
Source)
Fig. 8.1 Electrical Connections – Calibration
