ENDEVCO
www.endevco.com Tel: +1 (866) ENDEVCO [+1 (866) 363-3826]
IM133, Page 17
®
7. Calibration
This special mode selection allows the user to manually calibrate the unit.
This special mode is selected by pressing the “Select Function” push button while simultaneously
pressing the LEFT and RIGHT EDIT push buttons. When this special mode is selected the first
“Function LED” will be blinking and the first calibration constant for the selected channel will be shown
on the LED display. The settings of all of the functions will be saved in non-volatile memory when
entering this mode.
The user selects which calibration constant is being set by subsequently pressing the “Select
Function” push button. Each press of the “Select Function” push button will sequentially make one
of the “Function LEDs” blink indicating that the calibration constant is selected for programming and
the corresponding calibration constant will be shown on the LED display.
Pressing the “Select Function” push-button while the “Monitoring State” function LED is flashing
places the unit back into Normal mode. The calibration constants will be stored into the internal non-
volatile memory when the unit returns to the normal mode of operation. The settings for all of the
functions will be restored using the new calibration constants when the unit returns to the normal
mode of operation.
A checksum for the calibration constants is also stored in non-volatile memory. The unit will use this
checksum at power up to verify that all calibration constants are good. The unit will declare an error
if the checksum test for the calibration constants fails.
A cross-reference table between the calibration constants and the “Function LEDs” is shown below
(the input select and gain settings for each calibration constant is also shown).
Function LED
Calibration Constant
Input Select
Gain
1. Input Select
k1 for 100 < Gain < 1000
Volt
200
2. Current Exc. (mA)
k2 for 10 < Gain < 100
Volt
20
3. Sensitivity
k3 for 0 < Gain < 10
Volt
2
4. Output Scaling
k4 for 0 < Gain < 10
Chrg
2
5. HP Filter
k7 for 0 < Gain < 10
Chrg
2
6. LP Filter
k5 to calib. slope of A/D
Chrg
2 & 1
7. Monitoring State
k6 to calib. offset of A/D
Chrg
2
a)
Gain Calibration
Calibration constants k1 through k4 and k7 are used to calibrate the gain of the unit. This is
accomplished by applying a 300 Hz calibration signal into the ISOTRON input for k1, k2, and k3,
or into the Charge input for k4, and adjusting the calibration constant displayed on the LED display
until the desired output (input signal multiplied by gain) is obtained. The amplitude of the input
signal should be set to 30.0 mVRMS for k1, 0.300 VRMS for k2, 3.00 VRMS for k3, 3000 pC-RMS
for k4 and k7 (3.0 VRMS into a 1000 pF series capacitor).
b)
A/D Calibration
Calibration constants k5 and k6 are used to calibrate the Analog to Digital converter of the unit.
The following procedure must be followed to accomplish this calibration:
