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Using the Amper as a Pulse Data Logger

Automation Solutions Logger Collects Pulse Counting Data

The Amper family of data loggers provide an ability to measure and log pulse counts. As a pulse logger, it will no longer store a continuous stream of analog "level" data points, but instead will count the number of excursions the input signal makes above and below a preset point. The count will actually be double the number of ‘pulses’ seen as it captures edges, which are used by some types of equipment. Rather than keeping one single total count the Amper will put accumulated counts into time ‘buckets’, each of which is then stored on the data card. For example, if the bucket time is set to one hour then each day a data file will be written that contains 24 lines, each line containing the number of counts that occurred during the respective hour. A bucket time of one minute would result in files with 1440 lines per day. These data files can provide very useful data, as pipeline flows, energy usage, traffic patterns and other parameters may easily be analyzed by times as well as by simple totals. The fastest rate that may be correctly sampled is 10 pulses or 20 edges per second.

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How to Configure The Amper Logger to Log Pulse Counts

The Chartlogger Software will display the pulse counting results once 2 configuration files are created. Using a text editor ( ie. NotePad) create 2 text files: bucket.txt and pulse.txt.

The bucket.txt file contains the bucket time in seconds (60 to 3600). Bucket times start when the card is inserted. The daily results file will append each recording based on your chosen bucket, or recording interval (3600 sampling interval = 24 lines). The daily files will be identical to the standard "analog" data files.

The second file, called pulse.txt contains a number from 1 to 20475. This number represents the threshold in raw Amper Units for pulse detection. The pulse count increments every time (+ve and -ve) this point is crossed. Typically this value would be approx 50% of the high input Voltage applied but is not critical at all since most pulse, switch, relay or opto devices would cause the applied Voltage to be present or absent.

Note that the Amper does not supply the contact or switch closing Voltage source, it must be supplied externally but may be any AC or DC source that the Amper is configured to monitor.

Some suitable pulse.txt values for the millAmper and microAmper are ……

milliAmper (4-20mA nominal input): 820 would set the threshold at 4mA, 2048 at 10mA
microAmper with 332K resistor in series (50 Volt full scale input): 1000 = 2.5V threshold, 2000 = 5V threshold, 2400 = 6V threshold, 4800 = 12V threshold.

The applied Voltage could also be measured by the Amper in normal logging mode then the average reading halved to obtain a suitable threshold.

Since the Amper has an adjustable threshold it may be also used for applications that typical pulse counters could not perform. For example, if the microAmper is monitoring AC line Voltage that is nominally 120 VAC the pulse threshold could be set to correspond to say 115VAC. Now it will store in the time stamped buckets a count of every line sag below 115V. The results are written to the data files in exactly the same format as normal data files so can be directly read and displayed with ChartLogger, or of course with excel or any text editor.

When in pulse mode the Amper will write to the data card at the end of every bucket time (even if the count was zero), so whenever the card is removed it will always contain the most up to date information. Pulses often need to be counted for extended time periods such as months but data accumulated in the mean time may be required before then. If the card is removed the data may be copied to a pc and provided the card re-inserted before the present bucket time expires (i.e. when the Amper tries to write to the card again) no data will be lost. The Amper will keep accumulating and retain an accurate count provided the card is re-inserted before the bucket time expires; therefore totals for extended periods may be accumulated and the data may also be collected during this time without loosing any pulse counts.     

To change back to regular analog logging rename or delete one or both of the bucket.txt and pulse.txt files on the card, or use a card that does not have these files. The pulse configuration files, bucket.txt, pulse.txt and hyster.txt will not be deleted by the Amper so by looking at the card the user may determine what mode the Amper is in.

The storage time while in pulse mode is effectively infinite since the data files are so small.