Cooper Instruments QSC484 Installation Manual

QSC 484

LINE POWERED SIGNAL CONDITIONER

WITH ZERO CLAMPING AND AC OR DC

COUPLED OUTPUT

USER’S GUIDE

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CONTENTS

1.0 INTRODUCTION....................................................................................................... 1

2.0 DESCRIPTION.......................................................................................................... 1

3.0 OPERATION............................................................................................................. 2

4.0 SETTING THE CONSTANT CURRENT ................................................................... 3

4.0 MAINTENANCE AND REPAIR................................................................................. 4

5.0 SPECIFICATIONS .................................................................................................... 4

6.0 WARRANTY REPAIR POLICY................................................................................. 5

CF 102 ii 20141 rev. A

1.0 INTRODUCTION

The QSC 484 Power Unit features four operating configurations:

• AC-Coupled Mode

• AC-Coupled Mode with Active Clamp

• AC-Coupled Mode with Relay Clamp

• DC-Coupled Mode

The unit supplies 2mA to 20mA of constant current to transducers or amplifiers, as well as deliver up to 10mA of
low impedance (50 ohms) output current via a unity gain buffer amplifier.

2.0 DESCRIPTION

AC-Coupled Mode (no clamp)

The AC-Coupled Mode is used for most normal measurements since long term thermal drifting of long time
constant transducers is nullified by the internal AC coupling. In this configuration the signal information (AC
voltage) is decoupled from the transducer bias level (DC voltage) and fed through a unity gain buffer amplifier.
The coupling time constant is approximately 1,000 seconds and is dependent of output load.

Since the output signal is not clamped, a repetitive pulse train will gradually drift downward and stabilize in time
with equal areas above and below signal ground (Figure 1).

Figure 1 – Repetitive Pulse Train, AC Signal

To operate in this mode, set the MODE switch to AC, and the CLAMP switch to the OUT position.

NOTE: The front panel ZERO ADJUST knob has no effect in any of the AC mode configurations.

AC-Coupled Mode with Active Clamp

In this configuration, the conditioner is internally set to automatically keep pulsating output signals ground based
(within 20mV negative undershoot) and positive polarity. (Figure 2) This clamp is useful in stabilizing output
signals when interfacing with instrumentation that requires repetitive pulse train signals be ground based and of
one polarity (usually positive).

Figure 2 – Positive Polarity, Zero-based AC Output

CF 102 1 20141 rev. A