Ronan X96S WEIGH SCALE Manuel d'utilisateur télécharger pdf (Page 55)

ION Chamber

Detector/Amplifier Ronan’s ion chamber detector is filled with an inert

Assembly high-pressure gas. It uses low-voltage (-15VDC) bias

and generates a low-level current proportional to the gamma

radiation incident on the detector. The current

(DET-7471-XXX) generated is on the order of 10 ρA, so an electrometer amplifier is

required to convert the current to a low-impedance, high level

voltage signal. The signal is then measured by the X96S

Microprocessor, which converts the voltage signal to a output of

4-20mA for a specified measuring range.

Refer to drawing B-6409-K. The current (I), generated

Circuit Description by the ion chamber, is fed into the inverting input

terminal of the electrometer amplifieer, (IC1). The electrometer

amplifier output is filtered by R2C4 (a microphonic, low-pass

filter) and fed into a follower amplifier. The output of IC2 is

proportionally fed back to the inverting terminal to provide a

closed-loop gain based on the value of the gain resistance

potentionmeter (R2) on the X96S input board. (B-9742-K).

The detector’s gain is adjusted whenever the signal output of the

detector is too high and may saturate the input of the X96S, which

is approximately 3.5VDC. The output must be less than 3.0VDC

with an empty vessel.

An offset zero control (R6), used to null the offset voltage of the

electrometer amplifier, is factory adjusted and glyptal coated. R6

is adjusted to make the output, (TP1), zero with Rf shorted. (TP2

is circuit common.)

The most important components of the amplifier are the

operational amplifier (IC1), feedback resistor (Rf), and feedback

capacitor (Cf). If these components are substituted, the

performance of the system will be adversely affected.

Reference:

B-6409-K

B-9742-K

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Ronan X96S WEIGH SCALE Manuel d'utilisateur Page 55