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Offering
a high-accuracy 4 1/2-digit display of true RMS current for four
ranges, this Digital Panel Meter (DPM)
is intended for AC applications where there is considerable waveform
distortion from nonlinear loading. See, for example, the following
application:
The
2169's input is AC-coupled to read only the AC component, such as ripple
on a power supply.
The
model-numbering system is given in the Specifications
table, below.
The
meter uses precision circuitry to compute the root-mean-square value of
complex waveforms from 10 Hz to 10 kHz.
Spikes of up to 2.4 times the maximum of each input range are
accurately measured. This
provides a crest factor (Vp/Vrms) of 240 for a
signal amplitude of 1% of full scale, decreasing to 2.4 at 100% of full
scale.
5-A
input capability allows the output of 5-A current transformers to be
applied directly to the meter, with no need for a step-down
transformer. The current reading can easily be scaled to display the
input to the current transformer. Digital scaling and calibration
eliminate zero and span drift associated with potentiometers in
non-microcomputer based meters.
While
observing the same high-speed A/D conversion rate as all other 2000 Series
DPM's, the Model 2169's settling time and control response to a step
change in AC amplitude are limited by the RMS converter circuit to
approximately 1 second.
Typical
2169 accuracy is 99.9% of full scale (decreasing to 99.8% for low
frequency at high amplitude, or high frequency at low amplitude. The
following graph shows maximum full-scale error as a function of frequency
and signal amplitude. Error is 0.1% of full scale over all frequency
ranges of interest to AC power measurement. Error increases to 0.2%
at low frequency and high amplitude, or at high frequency and low
amplitude. Increasing in inverse proportion to signal amplitude, the
maximum crest factor is 2.4x.

All
current ranges are calibrated at the factory, with calibration factors for
each range stored in internal EEPROM.
This allows ranges to be changed in the field without having to
recalibrate the meter.
As
with all 2000 Series DPM’s, the peak value of the input signal is
automatically captured and may be displayed
via front-panel push button or a control signal received at the rear
connector (since the last meter reset). Data readings and outputs can be separately selected to be
either filtered or unfiltered.
See Digital Panel Meters (DPM’s)
for a full description of these and other standard DPM features.
2000
Series options applying to the RMS current meter include
AC
(RMS) Current Meter Specifications [Top
]
(Click
here for 2000 Series General Specifications)
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Model
Number
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AC
Current
Range*
|
Resolution
|
Input
Ohms
|
Error
(typical, at 25°C,
for all ranges)
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2169-2
|
2.0000 mA
|
0.1 μA
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100 Ω
|
0.1% of full scale ± 10
counts, 10 Hz to 10 kHz
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2169-20
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20.000 mA
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1 μA
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10 Ω
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2169-200
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200.00 mA
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10 μA
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1 Ω
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2169-5
|
5.000 A
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1 mA
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0.01 Ω
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All AC
Current Models
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Span
Temperature Coefficient |
±0.005% of
reading/°C |
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Zero
Temperature Coefficient |
0.1 count/°C |
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Crest
Factor |
2.4x at 100% of
full scale |
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RMS-to-DC
Conversion Settling Time |
1 second |
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Normal-Mode
Rejection at 50/60 Hz |
90 dB with minimum
digital filtering |
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Common-Mode
Rejection from DC to 60 Hz |
130 dB |
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* 1% to 100% of
full scale |
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