Fluke PM6681R Controller Synchronization, Measurement Cycle Synchronization, Introduction, Start

How to Measure Fast

Introduction

The CNT-8X counters can complete a measurement cycle in many different ways, each with its own advantage. This means that your first step is to select a ba- sic “measurement scenario” based on the requirements of the measurement. This chapter contains some measurement sce- narios that you can choose from.

These counters can measure with impres- sive speed if you program them correctly. You will find guidelines for speed im- provements in each of the described mea- surement scenarios.

Controller Synchronization

The start of measurements can either be individually or block synchronized by the controller. The instrument-to-controller synchronization deals with how to start a measurement or sequence of measure- ments and to read data in the most effi- cient way. You can also synchronize the measurement with the measuring object more accurately by using external control (arming), but this is not described here.

Measurement Cycle

Synchronization

It is a good practice to check that the measurement proceeds as planned when the controller has started a measurement, or block of measurements.

￿Start

If the input signal fails, or there is no arming etc., the measurement cycle will not start.

Timeout

Turn on timeout and set the time longer than the expected measurement cycle. Then wait for the timeout period, and take actions if you got timeout.

If the measurement time is long, you may have to wait many seconds or even min- utes until timeout, just to learn that the measurement never started.

Measurement started

Before starting a measurement, set up the status reporting system so that you get a

Service Request on Measure- ment-in-progress, bit 4 in the Operation Status Event Register. Check this with se- rial poll after a reasonable time when the measurement ought to be started, lets say after 100ms (time dependent on input sig- nal frequency). If the bit is true, continue. If false, abort the measurement and check the signals, alert the operator etc.

￿Stop

You must also know when the measure- ment is completed in order to read out the results. Should you read results or send other commands before the measurement is completed, the measurement will be in- terrupted.

You can of course let the controller wait until you are absolutely certain that the result is ready, before you fetch it. But it is better to use *OPC to get an Operation Complete status message, or *OPC? to get an ASCii “1” in the output queue, when the measurement is ready.

*OPC and *OPC? are common com- mands described on page 9-124and 9-125.

7-2 Introduction