HP 8-Channel 196 kSa/sec Digitizer plus DSP E1433A Tachometer Description, Tachometer Inputs

HP E1433A User's Guide

The Tachometer Option

Tachometer Description

A tachometer input can be included with the HP E1433A 8-Channel 196 kSa/sec Digitizer plus DSP as Option AYF. (It cannot be installed with a Source, Option 1D4.) The Tachometer Option is a two channel tachometer input used to capture the contents of a freerun counter whenever an external input crosses a programmable threshold.

Tachometer Inputs

The tachometer has two inputs which connect to analog conditioning, holdoff, and FIFO circuitry. See the block diagram in this chapter. The inputs can be configured so that one input connector (Tach 2) becomes an external trigger input and the other (Tach 1) remains a tachometer input. (The Tach 1 connector cannot be a trigger input.) The switch that determines this configuration is controlled by software.

External Trigger Input

An HP E1433A without a tachometer option can accept a TTL external trigger signal (see “Trigger Lines” in the chapter titled “Module Description”). With the tachometer option the HP E1433A still has that capability and is also able to accept an analog external trigger signal at the Tach 2 input.

Trigger Level

The trigger level of the tachometer can be set by software.

Tachometer Monitoring

The tachometer is capable of sending its analog input signal onto the HP E1433A module’s internal calibration line. The calibration line can be connected to the 196 kHz 4-channel input assembly, so that the signal on the tachometer’s connector can be monitored via an input channel. This can be useful when deciding where to set the trigger level of the tachometer. An example program is supplied with the HP E1433A Host Interface library, which shows how to perform this tachometer monitoring.

Exact RPM Triggering

The tachometer can be used to create exact RPM triggering, controlled by software. The RPM of the tach channel is calculated from tach transition times. Then the sample numbers in the data FIFO are determined for exact RPM triggering.

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