beautypg.com

Tachometer description – HP VXI E1432A User Manual

Page 129

background image

Tachometer Description

A tachometer input can be included with the HP E1432A 16 Channel 51.2
kSa/s 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 E1432A 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 E1432A 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
E1432A module’s internal calibration line. The calibration line can be
connected to the 51.2 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 E1432A 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.

HP E1432A User's Guide
The Tachometer Option

7-2

Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com