MODELS 483C30, 483C50, 482M179 AND 483M217 GENERAL OPERATION MANUAL
6
2-5.1. Programmable Gain
Adjustable incremental gain (from 0.1 to 200) is standard in these models. The steps in the incremental gain are 0.1.
This is particularly useful in the standardization of groups of sensors. Consider the following example, wherein the user
desires to normalize sensitivities to 1 V/unit for each channel.
Channel
Sensor Sensitivity
Gain Setting of Unit
Actual Gain Needed
1
st
10.10
mV
/
unit
99.00
99.01
2
nd
101.32
mV
/
unit
9.9
9.869
3
rd
22.30
mV
/
unit
44.8
44.84
The gain is set via the computer interface command set (See the command strings in Section 3-0 in the Computer
Interface Programming Guide.)
2-6.
Normalized Output Sensitivity
The definition of normalized output sensitivity is the calculation of the individual channel’s gain, depending on the
sensitivity of the sensor attached and the desired output sensitivity. This is simply a function of the desired output
sensitivity (in Volts/ unit) divided by the sensor’s sensitivity.
Gain =
1 Volt
/
Sensitivity (mV/unit)
Additionally, a feature to improve flexibility allows changing the output level to a value of 5 Volts/ unit instead of
normalized 1 Volt/ unit. Some users request the ability calculate the gain using a known input signal along with the
sensor sensitivity, and desired output level. The result of the request impacts the formula:
Gain =
1 Volt/
/
[Sensitivity (mV/unit) * Full Scale Input (units)]
Adding some simple error checking to insure the limits of the sensor and gain limits of the signal conditioner are not
exceeded completes the normalization process.
Gain
normalized
=
FSOT (V)
/
SENS * FSIN
Additional Considerations:
The storage of individual channel gains is stored in non-volatile memory locations. The new variables for each channel’s
sensitivity, Full Scale Output level, and Full Scale Input are stored in non-volatile memory locations when SAVS
command is sent to the unit.
The error checking should provide a flag if the desired normalized output level is not feasible due to gain limitations.
The gain required may be too large given the sensor sensitivity defined, or too small which implies the sensor will not be
capable measure the expected value. The typical sensor will output a signal up to
±
5 Volts. The maximum swing may be
used in the error checking.
The 483C30 and 482M179 models have the capability to provide signal conditioning for charge mode sensors in
addition to the standard ICP
type. The sensitivity (mV/ pC) of the charge conversion will allow charge mode sensors
(pC/ unit) to be normalized.
2.7. Overload Detection and Autoscaling
