Date: Wed, 10 Aug 2011 11:08:41

Author: --- "Brian Holton"

Subject: Re: Extech DMM Question

Post:

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I

V meter

V total

R

R meter

=09

10.0

0.043

0.99

98.9

4.3

=09

19.6

0.085

1.94

99.0

4.3

=09

29.2

0.128

2.80

95.9

4.4

=09

40.9

0.182

4.00

97.8

4.4

=09

49.8

0.224

4.80

96.4

4.5

=09

60.0

0.275

5.80

96.7

4.6

=09

70.0

0.329

6.80

97.1

4.7

=09

80.7

0.390

7.90

97.9

4.8

=09

90.0

0.450

8.80

97.8

5.0

=09

100.8

0.525

9.90

98.2

5.2

=09

110.9

0.607

10.80

97.4

5.5

=09

120.4

0.720

11.80

98.0

6.0

=09

130.3

0.809

12.80

98.2

6.2

=09

140.0

0.970

13.70

97.9

6.9

=09

151.5

1.187

14.80

97.7

7.8

=09

160.0

1.557

15.60

97.5

9.7

=09

170.0

1.978

16.60

97.6

11.6

=09

180.6

2.300

17.70

98.0

12.7

=09

=20

=20

From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On =
Behalf Of George M. Caplan
Sent: Wednesday, August 10, 2011 10:10 AM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] Extech DMM Question

=20

Thanks for the comments so far.

I am *not* using this meter to measure the waveforms of the stepper =
motor.

Sorry, I didn't make that clear.

I *am* using it to measure DC milliamps in a simple circuit with some =
#48 bulbs.

I expected a constant resistance.

If I have time, I will do more measurements today. In any case, my =
readings seem to correspond to those of Brian H. (although I did not get =
the attachment).

The Fluke "burden voltage" corresponds to a fixed resistance for a given =
scale, which is what I'd expect. 11 mV/mA is 11 ohms, which is =
(obviously) constant, but it's higher than I would have guessed. Anyway, =
for the Extech I expected a constant value for a particular range =
setting. Since the value is not constant, the meter can clearly affect =
the circuit more than I realized .. and in a somewhat unpredictable way.

I apologize for this email rambling. I am trying to do three projects at =
once, so I can't focus all my thought on one. I am sure none of you have =
ever had that problem.

=20

George









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IV meterV totalRR meter10.00.0430.9998.94.319.60.0851.9499.04.329.20.1282.8095.94.440.90.1824.0097.84.449.80.2244.8096.44.560.00.2755.8096.74.670.00.3296.8097.14.780.70.3907.9097.94.890.00.4508.8097.85.0100.80.5259.9098.25.2110.90.60710.8097.45.5120.40.72011.8098.06.0130.30.80912.8098.26.2140.00.97013.7097.96.9151.51.18714.8097.77.8160.01.55715.6097.59.7170.01.97816.6097.611.6180.62.30017.7098.012.7 From:=
=
tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On =
Behalf Of George M. CaplanSent: Wednesday, August 10, =
2011 10:10 AMTo: tap-l@lists.ncsu.eduSubject: Re: =
[tap-l] Extech DMM Question T=
hanks for the comments so far.I=
am *not* using this meter to measure the waveforms of the stepper =
motor.S=
orry, I didn't make that clear.I=
*am* using it to measure DC milliamps in a simple circuit with some #48 =
bulbs.I=
expected a constant resistance.I=
f I have time, I will do more measurements today. In any case, my =
readings seem to correspond to those of Brian H. (although I did not get =
the attachment).T=
he Fluke "burden voltage" corresponds to a fixed resistance =
for a given scale, which is what I'd expect. 11 mV/mA is 11 ohms, which =
is (obviously) constant, but it's higher than I would have guessed. =
Anyway, for the Extech I expected a constant value for a particular =
range setting. Since the value is not constant, the meter can clearly =
affect the circuit more than I realized .. and in a somewhat =
unpredictable way.I=
apologize for this email rambling. I am trying to do three projects at =
once, so I can't focus all my thought on one. I am sure none of you have =
ever had that problem. G=
eorge
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