Monarch Instrument DC1250 - Manual (Page 5)

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1.0 INTRODUCTION
This instrument is a versatile Solid State Data Recorder / Panel Indicator. It has all the
capability of a traditional paper recorder - variable chart speeds, the ability to review historic
data, see trends and more, with a number of specific exceptions - NO PAPER to jam, no
ink to smudge and no pens to clog or break. The data is stored in a Compact Flash
memory card, which can be easily transported.
Of course it does all the regular functions a lot better, and the data can be transferred
directly into reports, spreadsheets or analysis programs. Data can be examined and
archived on any Windows XP
TM compatible machine and can be printed out in various
formats as required.
This instrument has two universal inputs so it can measure voltage, current, thermocouples
and RTDs by simply selecting them from the menu. It also has two potential free alarm
output contacts and an isolated digital input. The display can be user configured to
graphics, digital or a combination. Maximum data storage is 2 Gigabytes. Communication
options include USB and Ethernet ports.
Things are done a little differently in a paperless recorder and there are a few new
concepts that you may need to become familiar with. There are more features and
functions in this unit than you will probably use. It is recommended that you read this
manual in its entirety before attempting to use the instrument.
The balance of this introduction will attempt to introduce some of the more unique features
of this paperless recorder.
1.1 CHART SPEED TO SAMPLE SPEED
A major difference between paper and paperless is SAMPLE SPEED, which is analogous
to CHART SPEED in the paper recorder. There is an apparent chart speed, the rate at
which the samples appear to move across the Graphics Display, but unlike paper recorders
the display is made up of discrete data points, each of which is a distinct sample of the data
being measured. The rate of movement across the screen is thus a direct function of the
sample rate. The major factor in deciding what sample rate to select is to know how much
data is enough. In a paper recorder a chart speed of 1 inch per hour is fine for a process
that does not vary very quickly but would result in a thick blur if trying to record a 1Hz sine
wave. Unlike a paper recorder, every point recorded by the paperless recorder is uniquely
identifiable, no matter how dense it appears on the screen. It is always better to have too
much data than to have too little. The only consideration is the amount of space used in
the memory card.
To relate chart speed to sample rate we need to consider how we plan to reproduce the
data. The graphic LCD display has a density of 70 pixels (data points) per inch; a typical
dot matrix printer has 180 pixels per inch and a laser printer 300 pixels per inch. Thus to fill
one inch of the display in one hour we need to sample at a rate of 70 samples per hour, a
little over once per minute, however if this is now printed on a laser printer it will fill less
than 1/3 of an inch. It is the amount and quality of the data that counts. Another advantage
of the paperless recorder is that it can sample internally at 100 samples per second (one
every 0.01 seconds). These samples can be averaged or peaks or valleys can be detected
and then this data can be stored at the chosen sample rate.
Trial and experience will yield the best sample speeds for the application. Start with a faster
sampling rate than you think you will need; you can always slow it down in the future. As a
rule of thumb, one sample every 10 seconds should give the equivalent information that 1
inch per hour of chart paper would.
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