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Based
on the Model 4077 DC Strain Gage Instrument,
the Model 4K/PM-77 uses the analog ±peak
capture capability of the 4077 to provide a complete system for
detection, display, and evaluation of real-time signal peaks in all kinds
of industrial operations. It is particularly useful in compressing,
crimping, and swaging operations (see the typical application
illustrated below).
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Capturing
Press Peak Values |
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Analog
Peak Capture Function of the Model 4K/PM-77 |
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The
Peak Monitor is capable of 8-millisecond "true analog" peak
capture and track, with indefinite digital hold. Faster
processes can be monitored by means of a special "peak
trend modification" of the Model 4K/PM-77 (described below).
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Functions
Provided by the
MODEL 4K/PM-77 "STANDARD
CONFIGURATION"
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Bargraph
indication of LOW PEAK and HIGH PEAK setpoints |
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Front-panel
buttons for display of either "LIVE" DATA or PEAK
VALUE |
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Front-panel
button for initiation of HARD-COPY OUTPUT
("DUMP") |
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Front-panel
button for AUTO-ZERO function |
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Front-panel
indicator lights when a peak is captured |
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Each
captured peak is monitored for conformance to preset limits,
and issues isolated TTL-level "GO—NO GO" logic
outputs for immediate process control |
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Each
captured peak can be reset either manually, by
front-panel button, or automatically, by external logic
command |
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A
special "history memory" stores the last 50
peaks, and can be "dumped" at any time from the
4K/PM-77's Interface Port |
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Scaled
±10
VDC analog output for strip-chart recording, etc. |
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A
special modification of the 4K/PM-77 provides monitoring of peak
trends in cyclic processes that are too fast for conventional
analog peak capture. Typical applications involve the
monitoring of tool or material wear (wear and metal fatigue
of dies, presses, bearings, bushings, etc.).
The
average value of the peak-capture channel (shown in the
following diagram) is available at all times for both bargraph and
digital display.
Representing
the trend of rapidly successive peaks, this value can be correlated, in
turn, to an average press force or other parameter, and can be evaluated
for conformance to preset limit values, with corresponding logic control
outputs. In
the peak-trend modification of the 4K/PM-77, the decay rate for the
analog peak memory is adjustable by the user from 1 mV/sec to
approximately 500 mV/sec (for a +10 VDC full-scale conditioned
signal). As can be seen in the above diagram, the continuous decay
of the peak-channel value permits capture or rapidly successive peaks of
similar amplitude without having to invoke a "RESET" command for
each peak.
Peak
Monitor Specifications [Top 
]
(Click
here for
4000 Series General
Specifications; see also
the statement
on Daytronic accuracy specifications)
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Number
of Inputs |
One |
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Input
Type |
Conventional
4-arm strain gage bridge, nominal 120 Ω or higher NOTE:
1/4- and 1/2-bridge gage configurations can be accomplished by means
of the Model 10CJB-2 Bridge Completion Card,
or by equivalent external bridge completion circuitry supplied by the
user.
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Input
Range (full-scale) |
1.5
or 3.00 mV/V* |
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Excitation
Supplied |
Selectable
5 or 10 VDC, nominal; ±80 mA maximum |
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Normal-Mode
Range |
±50
mV peak operating; ±8 V without instrument damage |
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Common-Mode
Range |
±0.25
V peak operating; ±8 V without instrument damage |
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Common-Mode
Rejection Ratio |
-90
dB at DC; -120 dB at 60 Hz, 1 kHz, and 3 kHz |
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Input
Impedance (Differential and Common-Mode) |
Greater
than 100 MΩ |
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Offset |
Initial:
±0.02% of full scale
Vs. Temperature: ±20 ppm/°C
Vs. Time: ±10 ppm/month
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Gain
Accuracy |
±0.02%
of full scale ± 1 count LSD, typical, following calibration** |
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Gain
Stability |
Vs.
Temperature: ±50 ppm/°C
Vs. Time: ±20 ppm/month
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Analog
Peak Memory Decay Rate |
Does
not exceed 0.4% of full scale/second (e.g., with full scale of 20000
counts, decay rate will not exceed 8 counts/100 msec) |
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Analog
Filtering |
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Filter |
3-pole
modified Butterworth; -3 dB at 20 Hz; -60 dB at 220 Hz
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Step
Response Settling Time (Full-Scale Output) |
To
1% of final value: 60 ms
To 0.1% of final value: 80 ms
To 0.02% of final value: 125 ms
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*
Since channel zeroing is by digital techniques, no input balance control
is provided. The allowable input range, therefore, must include an initial
unbalance (which, in commercially produced strain gage transducers, is
negligible). Other transducers may have to be externally trimmed to
be used with the Model 4K/PM-77, if zero unbalance exceeds 20% of full scale.
**
Initial (uncalibrated) inaccuracy may be as great as ±0.05% of full
scale. Maximum error that could occur upon replacement of the Model
4K/PM-77 not followed by calibration is ±0.1% of full scale. |
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