Line Frequency Filter Adjustment; Introduction; Procedure - Ametek 7124 Instruction Manual

Precision lock-in amplifier

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2.3 Line Frequency Filter Adjustment

20) Press one of the keys adjacent to the Start item. The procedure only takes a few

seconds and it does not matter if any BNC cables are attached or not attached.

Once it has finished, press the Main Display key.

21) The right-hand side of the display should now indicate R, the vector magnitude,

close to 100% of full-scale (i.e. the sinusoidal oscillator output, which was set to

1 kHz and a signal level of 0.5 V rms by the Auto-Default function, is being

measured with a full-scale sensitivity of 500 mV rms) and , the phase angle, of

near zero degrees, if a short cable is used.

Best results are obtained by allowing about one hour for the two units to warm up.

After this time we you should re-run the fiber calibration. It is also necessary to re-

run this if the power to either unit has been switched off and on again.

This completes the initial checks. Even though the procedure leaves many functions

untested, if the indicated results were obtained then the user can be reasonably sure

that the unit incurred no hidden damage in shipment and is in good working order.

The model 7124 incorporates a line-frequency rejection filter, which is normally

supplied set to 60 Hz. If the power line frequency of the country in which the

instrument is to be used is also 60 Hz then the setting does not need to be changed.

If, however, the unit is to be used in an area with a 50 Hz power line frequency the

setting should be changed using the following procedure.

1) Turn the model 7124 RCU power switch to the I (on) position.

2) Turn the 7124 main console power switch to the I (on) position.

3) The instrument's front panel display will now briefly display the following:-

Chapter 2, INSTALLATION AND INITIAL CHECKS

Figure 2-7, Fiber Calibration Menu

2-7

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