COND SGA-A & SGA-D Manuel_EN Rev3.doc
Page 14 on 20
Rev: 03/08/2006
d)
Check the calibration. Incorrect setting of the calibration Span switches are the most common cause of low
output - particularly when associated with ± Voltage outputs. Refer to the calibration instructions in Chapter
4. Refer to tutorial on the calibration set-up.
e)
Check the Zero (offset) is correct for the sensor. This too is a common reason for low outputs.
5.3.
High output
This is when an output is present but higher (in span or zero) than required.
a)
Check the sensor is connected (typically reading 350 Ohm across Strain and – and also
b)
Strain Input + and – of J2) with the power off.
c)
Check the Excitation voltage (J2) is at 10V DC
d)
Check the Zero (offset) is correct for the sensor. This is a common reason for high outputs where the offset
is either omitted or incorrect for the sensor. Refer to the calibration instructions in Chapter 4
e)
Refer to tutorial on the calibration set-up
f)
Check the calibration. Incorrect setting of the calibration span switches is the most common cause of low
output - particularly when associated with ± Voltage outputs.
5.4.
Unstable Output
This is when the output is unstable or varies. The cause could be (a) poor installation or (b) a noisy
environment.
5.4.1.
Poor Installation
This is when an output is present but higher or lower (in span or zero) than expected:
a)
Check the installation for problems and repair where necessary
b)
Poor termination
c)
High resistance on cable leads
d)
Low insulation impedance
e)
Proximity to High Voltage Equipment – Transformers, Contactors, Motors etc.
5.4.2.
Noisy Environment
a)
Check if the source can be found and remove noise
b)
Check the cable screening and ensure it is correctly installed and terminated
5.5.
Calibration
This section assumes that the unit is providing an output that is not stuck at top or bottom of the scale.
(See paragraphs 1 to 4 if this is the case)
Ensure you have the calibration set-up correctly installed i.e.mV source and output as required.
Ensure you are connected to the correct sensor and not to another adjacent unit.
Ensure you have the correct calibration data from the sensor manufacturer. This must include a certified table
with offset, zero and linearity.
Ensure the temperature and other environmental parameters are within specification and where necessary
taken into account when calibrating should such parameters have an effect on the calibration.
5.6.
Fine Span (Gain) and Zero (Offset) Adjustment Problems
If the adjustment cannot reach the maximum output desired then, check the tare is not too high.
If the potentiometer does not alter the output the unit must be repaired – remove from service.
It is always wise to check a known good COND COND SGA against the problem installation before rejecting
the suspect COND COND SGA.
