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| Counter Meter |
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Model 2140(R) | ||||||||||||||||||||||||||||||||||||||||
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This extraordinarily versatile dual-channel Counter Meter can perform a wide variety of functions, particularly when it is equipped with the "R" OPTION ("EXTENDED DUAL-CHANNEL COUNTER"). Each
of the following 2140 / 2140R functions is described separately
below. General 2140
Specifications (applying to all modes of operation) are also given
below.
In general, the 2140's two channels can accept PNP or NPN outputs from proximity switches and other pulse-generating industrial transducers; TTL or CMOS logic signals; magnetic pickup pulses down to 12 mV; contact closures; low-level outputs from all types of turbine flowmeters; or AC line inputs of up to 250 V-AC. The inverse period technique is used to calculate frequency or rate up to six places, and with an update as high as 25/s (see General Counter Meter Specifications). Nine hysteresis pairs are jumper selectable for reliable triggering with different signal levels. Low-pass filtering for noise reduction and contact debounce times are selectable (see Specifications, below). The 2140's six-digit display can show any value from -999,999 to 999,999 with programmable decimal point. Scaling allows direct readout in desired engineering units (e.g., gallons or cubic feet based on counts from a turbine flowmeter). The channel to be displayed is selected via a front-panel pushbutton. 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). The built-in isolated excitation supply can power proximity switches and other sensors, if required. In addition to the "R" OPTION (discussed, where applicable, in the following sections), 2000 Series options applying to the Model 2140 Counter Meter include:
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| Dual-Channel
Up/Down Totalizing [Back
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In this basic operating mode of the Model 2140, each channel ("A" and "B") may be independently set up and scaled to count up from zero (or other value) to a preset limit, or to count down from a preset value to zero (or other limit).
Channel A can accept pulses ranging from 0.0025 Hz up to 2 MHz; Channel B, from 0.0025 Hz up to 250 kHz. Countdown operation is set up by entering a negative scaling factor. All totals are stored in nonvolatile memory.
The following figure shows Model 2140(R) system-level capabilities. Employing basic 2000 Series optional plug-in boards, the 2140 can independently scale, display, and alarm two totals, and the totals (plus alarm data) can be transmitted via RS232 or RS485. The displayed totals can also be transmitted as isolated 4-20 mA output and as parallel BCD output. Supplied with the "R" Option, the 2140 can further display and transmit arithmetic combinations of the two totals.
Here are some typical totalizer applications (in almost all cases, the 2140 in totalizer mode will be used with the Dual Controller Option ("A" or "B" Option)):
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When equipped with the "R" Option ("Extended Dual-Channel Counter"), the 2140 in totalizer mode has these further capabilities:
Simultaneous Display of Rate and Total
Channel A can display TOTAL for an input signal while Channel B displays RATE for the same signal. The selection of A or B for display is by front-panel push button. This mode is ideal for flow applications (as in the application Total and Rate Simultaneously).
Up/Down Counting with Count Direction Control
Channel A can serve as an up/down counter, where the count direction is dynamically changed by applying a signal to Channel B. For example, Channel A can count and scale pulses from a turbine flowmeter, while Channel B inputs the direction of flow. This allows total volume to be tracked in case of reversible flow (as in the application Up/Down Totalizing).
Totalizing with External Inhibit
Totalizing by Channel A can be temporarily inhibited by applying a signal to Channel B. For example, 60-Hz AC pulses can be counted by Channel A and be scaled to display elapsed hours. A signal can be applied to Channel B to start or stop pulse counting when a process is in operation.
Arithmetic Functions
The following cross-channel computations solve many application problems: A+B, A-B, A*B, A/B, and (A/B-1). For example, A+B allows two input flows to be summed for total volume (as in the application Combining Two Totals), while A-B allows outflow to be subtracted from inflow for net volume. The last two functions—A/B and (A/B-1)—are discussed in detail under the Ratio and Draw Measurement operation of the Model 2140R.
Linearization of Nonlinear Inputs
Exceptionally
accurate custom-curve rate linearization is achievable—for example, to
linearize the low flow end of turbine flowmeters.
For setup, up to 240 data points can be entered into a spreadsheet or
text file by the user. The computer
then calculates nonlinear segments, which are downloaded into the meter via
RS232 (assuming that an optional RS232 Interface Board
is present). The linearized rate
can then be totalized by the 2140R.
| Ratio
and Draw Measurement [Back
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NOTE: The RATIO and DRAW modes of operation require that the Model 2140 be equipped with the "R" Option ("Extended Dual-Channel Counter").
Here are some typical ratio and draw applications:
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In the RATIO (A/B) operating mode of the 2140R, the ratio of the two input signals ("A" and "B") is continuously calculated. The result can be used to compare flow rates in two channels, the RPM of rollers or gears, or the speed of moving machinery, such as conveyor belts—see the first four applications listed above.
Ratio can also be applied to scaled totals to compare two batches to be mixed. In this case, one meter is used to monitor the ratio of flow rates, and a second to monitor the resulting batch totals (for more details, see the Pulse-Input Batching operation of the Model 2140R).
DRAW (A/B-1) is obtained by subtracting 1 from the ratio A/B. This quantity is often used to measure the elongation or shrinkage of material as it passes between rollers, or to monitor variation in the speed of rollers for tensioning—see, the last application listed above.
In either RATIO or DRAW operation, Channel A can accept pulses ranging from 0.0025 Hz up to 2 MHz; Channel B, from 0.0025 Hz up to 250 kHz.
The
frequency of the input signal on each channel is first measured, and is then
converted to rate in engineering units by multiplying it by the appropriate
scaling factor for that channel. Either
rate can be displayed. The A/B
ratio is then determined mathematically by the meter, and 1 is subtracted for
draw. The result can be scaled by a
multiple of 10 from 0.0001 to 100000, and the decimal point can be set to
display the result with the desired precision (up to six digits).
Readings beyond 999,999 are expressed in XXXXEX scientific notation.
| Time
Interval / "Stopwatch" [Back
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NOTE: The standard version of the Model 2140 can perform the time-interval measurements described below. "Stopwatch" operation, however, requires that the 2140 be equipped with the "R" Option ("Extended Dual-Channel Counter"). In both timing modes of operation, Channel A can accept pulses ranging from 0.005 Hz up to 2 MHz; Channel B, from 0.005 Hz up to 250 kHz.
Here are some typical timing applications:
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Time Interval Operation |
As a time interval meter, the 2140 can be set to display
Average Time Delay
The 2140 can measure the delay between periodic pulses applied to Channels A and B. As shown in the following figure, timing starts when a pulse is applied to Channel A (selectable rising or falling edge) and ends when a pulse is applied to Channel B (selectable rising or falling edge).
Pulse Width
The 2140 can measure the width of a single pulsed signal when Channels A and B are tied together. This situation is shown in the following figure. A rising or falling edge may be selected to start the timing (the opposite edge must be selected to stop the timing).
Timing is achieved by counting 5.5-MHz clock pulses. Multiple integral time intervals are averaged over a selectable gate time (from 10 ms to 199.99 s). The gate time also controls the display update time (see General Counter Meter Specifications).
The
default display is in microseconds.
Display resolution down to 0.2 µs can be achieved by applying a
multiplier of 10, moving the decimal point by one position, and averaging many
time intervals. Resolutions up to 1
s or greater are also programmable.
When equipped with the "R" Option, the 2140 in STOPWATCH mode is able to time single events that produce start and stop pulses. It can also be used to time the width of a single pulse. These two situations are illustrated in the following figure.
The stopwatch display is updated during timing at a rate controlled by the gate time, up to 25/s. The display is reset to zero as soon as the next start pulse occurs. Accumulated time for all stopwatch-timed events is also tracked, and may be selected for display (up to 999,999 hours).
The event time may be displayed in standard HH.MM.SS clock format with 1 s resolution, or as hours, minutes, or seconds with six-digit resolution. Timing resolution is 1 µs, allowing measurement of any time interval from 1 µs to 99 hours.
In the upper portion of the above diagram, the 2140R measures the time interval between a START pulse on Channel A and a second (STOP) pulse on the same channel. This is the stopwatch "A to A" mode. Timing may be set to start and stop on either the rising ("positive") or falling ("negative") edges of the two pulses.
In
stopwatch "A to B"
mode, the time interval is measured between a START pulse on Channel A (rising
or falling edge) and a STOP pulse on Channel B (same edge polarity).
This mode allows inputs from different sources.
In addition, the A and B inputs can be tied together to start the
stopwatch with one edge polarity and stop it with the other (as in the lower
portion of the diagram).
| Phase
Angle and Duty Cycle [Back
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NOTE: The PHASE ANGLE and DUTY CYCLE modes of operation require that the Model 2140 be equipped with the "R" Option ("Extended Dual-Channel Counter").
Here are some typical phase angle / duty cycle applications:
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Phase Angle Operation |
Phase Angle indicates the lead or lag in degrees from 0° to 360° between two periodic signals having the same frequency. Measurement of phase angle requires that two signals with identical periods be applied to Channels A and B of the 2140R. A display from -180° to +180° is obtained by timing the rising edge of one channel and the falling edge of the other channel, and programming a 180° offset (see the following figure, in which phase angle = (360)P1/P).
A resolution of 1°, 0.1°, or 0.01° is selectable. The allowed frequency range is 0.005 Hz to 10 kHz. Accuracy is 0.01% up to 100 Hz, 0.1% at 1 kHz, and 1% at 10 kHz. The maximum timing interval is 200 seconds.
Phase angle measurement is commonly used with AC power from 50 to 400 Hz. Phase angle needs to be set to zero to synchronize AC generators (see the second application listed above). It also applies to the triggering of SCR's and Triacs for power control. The phase angle between AC current and voltage determines power factor. The 2140R provides exceptionally fast response and six-digit accuracy for low frequencies such as AC line frequency.
Phase
angle is determined by timing crystal clock pulses over a specified gate time
(10 ms to 199.99 s). By selecting
the minimum gate time of 10 ms, the update rate can be as high as 25/s for 50/60
Hz AC line frequency. Improved
accuracy can be obtained by making the gate time long enough to allow averaging
of multiple cycles.
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Duty Cycle Operation |
Duty cycle is a measure of ON or OFF period as a percentage of total period. As with phase angle, duty cycle is determined by averaging an integral number of periods over a gate time (selectable from 10 ms to 199.99 s).
The same signal is applied to Channels A and B (see the following figure). The 2140R divides the average pulse width by the period between pulses, expressing this ratio in percent. By selecting rising or falling pulse edges, the ON or OFF duty cycle can be displayed. Here, duty cycle = (100)t/P.
In this mode, a resolution of 1°, 0.1°, or 0.01° is selectable. The allowed frequency range is 0.005 Hz to 50 kHz. Accuracy is 0.01% up to 500 Hz, 0.1% at 5 kHz, and 1% at 50 kHz. The maximum timing interval is 200 seconds.
Duty cycle measurement is used to monitor modulated proportional control systems and pulse-modulated systems such as radar, lasers, or packet radio (see the first application listed above).
For
long periods, duty cycle can be measured by using the Dual-Channel
Up/Down Totalizing capability of the
2140 to totalize AC line cycles, and having the counter display the
"A/B" ratio of the two totals scaled to percent (as in the application
Machine ON Time and Utilization).
| Pulse-Input
Batching [Back
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NOTE: The BATCH CONTROLLER mode of operation requires that the Model 2140 be equipped with the "R" Option ("Extended Dual-Channel Counter").
Here are some typical batching applications:
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Operating as a high-speed batch controller, the Model 2140R accepts a wide range of pulse signals—in particular, those from turbine flowmeters—the same signal being applied in parallel to the instrument's "A" and "B" channels. It can then display (1) current batch total, (2) grand total or number of batches, and (3) flow rate. All displayed values are scaled to engineering units of volume or flow.
A 10-amp contact relay serves as the batch relay to control repetitive fill operations the single-relay board goes in the slot that would be otherwise available for the Analog Output Board). It repeats the batch cycles continuously with a delay between successive cycles which may be set from 10 ms to 199.99 s, or which may be based on an external control input. The batch total can be set to count up from zero to a preset limit (as in the first of the two figures given below), or down from a preset limit to zero (as in the second figure).
In the up-counting batch control shown in the following figure, the 2140R counts up from zero to a preset maximum. A "prewarn" level is available to slow down filling near the preset (to avoid overshoot). A time delay can be programmed from the end of each batch to the start of the next one.
In the down-counting batch control shown in the following figure, the 2140R counts down from the preset maximum to zero. A "prewarn" level is available to slow down filling near zero. Again, a time delay between successive batch cycles can be programmed.
The Dual Controller Option ("A" or "B" Option) is normally used in pulse-input batching by the 2140R. Either relay of the Dual Controller can be assigned to the batch total to serve as a prewarning (to slow down filling near the setpoint), or it can be assigned to the grand total or number of batches, or to the flow rate (see Using Three Relays to Control a Pump for a typical "three-relay" application).
An optional RS232 or RS485 Interface allows the 2140R to transmit any of the three measured variables, as well as flow-rate peak. If required, all four items can be displayed simultaneously by augmenting the 2140R with up to three Remote Displays. Each remote display can have its own optional analog output and dual relays for alarm and/or control.
In this mode of operation, the 2140R's "A" and "B" channels are used independently, as explained below. Either channel can accept pulse rates from 0.0025 Hz up to 250 kHz, which exceeds the working range of conventional turbine flowmeters.
Channel A is used for totalizing. The measured total is scaled mathematically for control and display in engineering units (such as liters).
Channel B is used for rate, as determined via the "inverse period" technique (see General Counter Meter Specifications).
For
either total or rate, displayed values can be up to six digits (999,999) with
selectable decimal point.
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