Transient Recorder; Frequency Response Measurement Using Curve Storage And Frequency Sweep - Ametek 7280 Instruction Manual

Chapter 6, COMPUTER OPERATION

6.5.05 Transient Recorder

6.5.06 Frequency Response Measurement using Curve
Storage and Frequency Sweep
6-38
As the acquisition is running, the M command reports the status of the curve
acquisition. Once this indicates the acquisition is complete (i.e. parameter 1 = 0,
parameter 2 = 1), the acquired data may be transferred to the computer using:
DC. 0 Transfers X channel output values in floating point mode.
DC. 1 Transfers Y channel output values in floating point mode.
The input routine of the program must be prepared to read and store 1000 responses
to each of these commands.
In this example, the signal recovery capabilities of the lock-in amplifier are not used,
but the auxiliary inputs are. The voltage applied to the ADC1 input on the rear panel
is sampled and digitized at a rate of 40 kHz, with the values being stored to the curve
buffer. Sampling is required to start on receipt of a trigger at the TRIG IN connector
on the rear panel and must last for 500 ms.
The sequence of commands is therefore as follows:
NC Clear and reset curve buffer
LEN 20000 500 ms recording time at 40 kHz = 20,000 points
TADC 6 Set ADC1 sampling to burst mode, fixed
rate (25 µs per point, or 40 kHz), external trigger, and arm
trigger
As soon as a trigger occurs, the acquisition starts. Once it completes the acquired data
may be transferred to the computer using:-
DC. 5 Transfers ADC1 values in floating point mode
The input routine of the program must be prepared to read and store 20,000 responses
to this command.
In this example, a more sophisticated version of that given in section 6.5.03, the
internal oscillator frequency sweep generator is used in conjunction with curve
storage, allowing the acquisition of a frequency response without the need for the
computer to perform the frequency setting function for each point.
As before, the lock-in amplifier's internal oscillator output signal is fed via the filter
stage under test to the signal input. The oscillator frequency is stepped between a
lower and an upper frequency and the signal magnitude and phase are recorded.
The required sequence of commands is therefore as follows:-
IE 0 Set reference mode to internal
VMODE 1 Single-ended voltage input mode
AUTOMATIC 1 AC Gain control automatic
FLOAT 1 Float input connector shell using 1 kΩ to ground