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Subject: pH meters

pH meters

From: Ralph Roessler <whenry>
Date: Thursday, March 23, 1989
>I'm also not certain whether crossing brands is problem free

I assume your swapping probes - the spec to check is the input impedance
of the probe, if they match you should be okay. \

RE: Analog vs Digital:  I may have oversimplified my response over the
telephone.  When I measure something static, I have no problem using an
inexpensive digital meter, and find it easier to use, however, if my
input is dynamic, unless you have a good (read expensive) digital meter,
it's very difficult to interpret your results.

If you decide to purchase a digital meter (pH, multi, or whatever), the
key specifications to look at are:

    1) Input Scan rate (in samples per second)
    2) Resolution (or accuracy, usually in bits of resolution.
    3) Input range (specified in Full Scale)
    4) Signal Conditioning available (e.g. electrical isolation,
        simultaneous sample & hold)

These specs make the meter and are buried under all the bells. They
determine how good the A\D converter is.  Of course, you need a probe
that can match this also.

                  Conservation DistList Instance 2:15
                  Distributed: Saturday, April 1, 1989
                        Message Id: cdl-2-15-001
Received on Thursday, 23 March, 1989

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