ENDEVCO 2680
INSTRUCTION MANUAL
IM2680
Page B-3
Therefore, if Ccal in Figure B-1 is exactly 100 pF, then:
Eout = Aq Ecal
If Ccal is other than exactly 100pF, use the following formula:
C cal
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Eout = Aq Ecal 1000
Adjusted to 3.85 mV/pC, as determined by formula. To calibrate the Charge Amplifier in a
practical application, set the Oscillator output (figure A-2) to some convenient value, e.g., Ecal =
200 mV rms. Assuming that series capacitor Ccal is exactly 1000 pf, the Gain of the Charge
Amplifier is adjusted until its output is:
Aout = Aq Ecal
= 3.85 X 200
= 700 mV rms
During Gain calibration the Oscilloscope must be monitored to ensure the Output Signal is not
clipped or distorted.
3.
REMOVAL AND RESEALING GAIN-ACCESS SCREWS
Charge Amplifiers used in calibrated airborne systems have the Gain-Access Screw Solder-
sealed to the case for operating in abnormal environments. The instructions provided in
paragraphs 4.3.2 and 4.3.3 are to be used when removing and resealing the access screw.
Endevco recommends only new screws be installed in Charge Amplifiers. Access Screws can be
procured from Endevco under part number 1103 (see Table B-1).
Table B-1 lists the equipment required to remove and seal the Gain-Access Screw, and to adjust
the Gain of the Charge Amplifier as defined.
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ITEM
PURPOSE
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Power supply, +20 to ±32 V dc, 50 mA max.
Source supply for Charge Amplifier
Oscillator, 3 Hz to 20 kHz
Input signal to Charge Amplifier
Oscilloscope, DC to 5 MHz
Monitor Charge Amplifier output signal clipping
Digital voltmeter (DVM)
Monitor Charge Amplifier voltage output
Capacitor, 1000 pF ±1%, shielded
Provide input capacitance to Charge Amplifier.
Endevco Model 2947 recommended
Soldering iron, Narrow Tip, 200 W
To solder-seal access screws to case
Rosin core solder, 63-37
To seal access screws to case
Oven, temperature minimum of +100°C
To preheat Charge Amplifier
Accessory Kit consisting of:
Allen Wrench, 5/64, with handle
Remove access screw. Endevco P/N EHM453
Allen Wrench, 0.05
Adjust gain Pot. Endevco P/N EHM35
Access Screws (two)
Seal gain-access hole. Endevco P/N 11003
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