Orbit Controls OC 7040A, Owner'S Manual

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7 CALIBRATION
7.1 Calibration of linear signals DC and AC
The calibration steps are described in §6, Service Menu and HtESt. Linear signals such as 4-20mA, 0-
1V can be calibrated as described.
7.2 Calibration of non-linear signals (Tables)
Input signals such as RTD Thermometer and Thermocouples will be linearized as follows:
7.2.1 Calibration of Pt-100 Thermometer
SEnS LinEAr
Set LO 0
Set HI 100
In the HtESt calibrate with 0 Ohm and 100 Ohm. After the
calibration is finished, switch OFF and ON again.
SEnS select Pt 100 in the Menu.
Switch into the measuring mode with ACK. The Display follows the
temperature of Pt-100 in a range from -200 to 600ºC.
7.2.2 Calibration of Thermocouples
Jumper Pt-100
H1
1 + 2
Z8 closed
Z9 open
H3 ---
R19 18k Resistor 1%
Jumper Thermocouples
H1
1 + 2
Z8 closed
Z9 open
H3 ---
R19 5k6 Resistor 1%
SEnS LinEAr
Set LO 0
Set HI 100
(100 = 100 mV)
In the HtESt calibrate with 0 und 100mV. After the calibration is
finished, switch OFF and ON again.
SEnS Select the required T/C in the Menu.
Switch into the
measuring mode with ACK. The Display follows the temperature of
the selected T/C within its defined range.
The cold junction is compensated with SMT160 connected to the
terminal block.
7.3
Calculation of R19
When the individual measuring range by using R19 is selected, following has to be considered:
The AD-C type LT2400 is designed for bipolar operation. Its zero reference point is set to +1.25V. Since
R19 determines the gain of the input amplifier INA118, its output signal (Pin 6) has to be within 0 and
2.500V for the full range of the input signal. For Zero input is Pin 6 = 1.25V. For maximum negative input
is Pin 6 = 2.500V. For maximum positive input is Pin 6 = 0V. It is important to calculate R19 such that the
signal swing at the output of INA118 (Pin 6) never goes bellow 0V and above 2.500V.
The calibration mode in the
HtESt shows the range of the input signal (§ 6). When zero signal is applied,
the display shows the reference voltage of 1.25xx V. With a maximum signal the display will show
2.500V. It is recommended to set R19 such that the display arrives at 2.2xxx with the maximum value of
the input signal. This will permit 10% overload of the input.
G = Gain
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