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post #14 of (permalink) Old 11-14-2011, 08:26 PM
Algae Grower
dundadundun's Avatar
Join Date: Apr 2010
Location: se, pa
Posts: 129
my inquiry...

To: tech support
Subject: sq sensor inquiry

from what i gather from the spec pages on these units, they can be used in conjunction with a decent multimeter.

my question would have to do with accuracy and difficulties associated with use in such a manner. i am curious as to whether a digital readout would be sufficient on a multimeter that reads at a minimum of 100 microvolts (.1 millivolt).

my concerns would be along the lines of whether the reading would be one such that would be rapidly changing so as to cause difficulty in relaying that information and displaying it in real time on a digital display of a multimeter.

another concern would be that in the case, the display would be sufficient... how would my accuracy be affected with a .1 millivolt capable multimeter vs. the purchase of a whole unit. say an MQ-200 for example.

now, from what i gather from the online manual, there is 3 wires on the sensor. of course my multimeter only has 2 usable prongs (+ and -). this leaves the question of whether or not the ground lead is necessary when used with a multimeter and if it can just be connected with the negative lead to facilitate a measurement.

from what i understand, the sensors calibration is set to 5.00 μmol m-2 s-1 per mV. my meter displays down to .1mV. i assume that gives me the possibility for a measurement down to 0.5 μmol m-2 s-1 per each 100 ÁV. would this be correct?

if there are any other complications, difficulties or work-arounds that may be necessary, please graciously inform me. i'm very interested in this product (SQ-120), yet feel it would be a waste to go as far as purchasing an MQ model given the relatively infrequent use that will be necessary for my purposes.

thank you very much for your time and patience with my thick skull,
the response...
my name,

A multimeter will work just fine for your application. The ground wire should be connected with the negative lead as you stated. Yes the accuracy is 0.5 μmol m-2 s-1 per each 100 ÁV.

Let me know if you have any other questions.

Skiffington Smith
Electrical Engineering Intern
so if you have a multimeter that can read .1mV than you can have an accuracy of .5 μmol using just the SQ-120 sensor for your tanks.

with a little searching, there shouldn't be a problem getting a multimeter capable of such measurements for under $80 if you don't already have one.
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