Tuttnauer E Series - 6. CALIBRATION OF TEMPERATURE AND PRESSURE; 6.1 Method of Calibration

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6. CALIBRATION OF TEMPERATURE AND PRESSURE
6.1 Method of Calibration:
The calibration of temperature and pressure is performed digitally.
The temperature and pressure measuring circuits are designed with
components having 1% accuracy.
The temperature circuit is linear and has an output of 100mV÷2400mV
for a temperature range 20°C÷150°C.
The pressure circuit is also linear and has an output of 100mV÷2400mV
for a pressure range 0÷400 kPa.
The measuring at the A/D is limited for values higher than 2400mV or
below 100mV.
The system has a non-volatile memory in which the offset and gain data
of the sensors are stored.
Calibration is performed by use of the keyboard (or the communication
port for computer use).
Following is a description of the calibration of temperature and pressure
using the keyboard. The calibration procedure is identical to all autoclave
models.
Definition of Gain and Offset:
Every straight line can be defined by the equation ax+b=y. “a” is the
deviation from y=0 and “b” is the slope of the line. In our case a=Gain
and b=Offset.
The system is based on calculation of offset and gain of two points as in
the following example
If the actual measured pressures are 100 kPa & 300 kPa and the
displayed pressures are 90 kPa & 310 kPa respectively, the ‘input Vs
pressure” graph will be as follows.
The calibration method enables to input this data into the system in order
to perform automatic correction of OFFSET and GAIN.
It is necessary to define the two points, which have to be input to the
system, prior to performing calibration.
a
X
Y
INPUT FROM SENSOR
PRESURE
V
1
310
300
V
2
100
90
READ
ACTUAL