The A/B ratio and A/B-1 draw meters are selectable operating modes of the Micro counter with Extended counter main board and FR dual-channel signal conditioner board.
Ratio 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. Ratio can also be applied to scaled totals to compare two batches to be mixed. In this application, one meter is used to monitor the ratio of flow rates, and a second meter to monitor the resulting batch totals.
Draw is obtained by subtracting 1 from ratio. Draw 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.
Ratio and draw are similar, except that 1 is subtracted from ratio to obtain draw. The frequency of channels A and B is first measured and is then converted to rate in engineering units by multiplying it by the appropriate scale factor for that channel. Either rate can be displayed. The A/B ratio is then taken mathematically by the meter, and 1 is subtracted for draw. The result can be multiplied by a multiple or 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.
Fast, High Resolution Measurement
The Micro counter determines frequency by timing an integral number of periods over a programmable gate time. The inverse period approach allows greater accuracy and faster update times than conventional meters which count signal pulses over a specified time interval.
Channel A accepts pulses from 0.005 Hz to 1 MHz, while Channel B accepts pulses from 0.005 Hz to 250 kHz. At the minimum gate time of 10 ms, update rates can be up to 25/second. Such fast response is ideal for peak capture and for alarm and control applications. Variations in the displayed reading can be reduced by selecting a longer gate time. An adaptive filter can further reduce variations due to noise while rapidly responding to actual changes in the signal.
Universal Signal Conditioner
The Micro dual-channel signal conditioner accepts inputs from proximity switches with PNP or NPN output, TTL or CMOS logic, magnetic pickups, contact closures, low-level outputs from turbine flow meters down to 12 mV , and high-level AC line inputs up to 250 Vac. Jumper selections provide optimum operation for different sensor types and noise conditions. A built-in isolated 5, 10, or 24 Vdc excitation supply can power proximity switches and other sensors, and eliminate the need for an external power supply.
High brightness red. Green available with 0.56" digits.
-999999 to +999999, XXXXEX scientific notation beyond 999999
Four LED lamps
AC, pulses from NPN, PNP transistors, contact closures, magnetic pickups
Common ground for channels A & B
Channel A Frequency
0.005 Hz to 1 MHz
Channel B Frequency
0.005 Hz to 250 kHz
-12 mV to +12 mV, +30 mV to +60 mV, -30 mV to -20 mV,
-150 mV to +150 mV, +350 mV to +600 mV, -600 mV to -350 mV,
-1.15V to +1.15V, +1.25V to +2.1V, -2.1 V to -1.25V
Selectable: 1 MHz, 30 kHz, 250 Hz
Selectable: 0, 3, 50 ms
Gate time + 30 ms+ 0-2 signal periods
Selectable 10 ms to 199.99 s
Max Signal Wait Time
Selectable 10 ms to 199.99 s
Output & Display Updates
Same as conversion time
Crystal calibrated to ±2 ppm
±1 ppm/°C (typ)
95-240 Vac ±10% and 95-370 Vdc
12-34 Vac and 10-48 Vdc
DC or 49-440 Hz
Safety-rated to 250 Vac, meter ground to earth ground,
DC to 60 Hz, 4.2 kVp per High Voltage Test
5 Vdc ±5%, 100 mA max
10 Vdc ±5%, 120 mA max
24 Vdc ±5%, 50 mA max
50 Vdc to meter ground
0°C to 60°C
-40°C to 85°C
95% at 40°C, non-condensing
NEMA-4X (IP-65) when panel mounted
Controlling the Mixing Ratio of Two Fluids
Displaying and alarming the input flow rate ratio of two fluids (gas or liquid) allows these to be mixed in a predetermined ratio in continuous processes. The sensing element is normally a turbine flowmeter, which outputs pulses at a frequency proportional to flow rate. The A/B ratio can also be displayed for totalized rate (or delivered volume).
Comparing Fluid Inflow & Outflow
The ratio of the inflow and outflow rates of a tank is a measure of the relative filling or emptying rate. The same meter can also be programmed to display the net inflow or outflow rate in flow units, or to display totalized inflow our outflow in volume units. Any of these parameters can be alarmed using the dual relay board and be transmitted via 4-20 mA, RS232 or RS485.
Controlling Coating Thickness on a Film
In this application, Channel A measures the rate at which a coating material is applied, as measured by a flow meter, while Channel B measures the speed of the film based on pulses from a proximity switch. Displaying and alarming the A/B ratio assures that an even thickness of coating material is applied as the speed of the film is varies.
Synchronizing Two Conveyor Lines
The dual-channel Micro counter can measure the speed of conveyor lines by using the output of proximity switches which sense gear teeth or spokes of rotating drive wheels. Displaying the speed ratio of two lines allows line speeds to be adjusted so that material arrives at work stations when needed.
Measuring Draw for Elongation
Draw (Ch A / Ch B – 1) can be used to display the elongation of films compressed between rollers, the shrinkage films, and the RPM difference of rollers whose speed is varied to maintain tension. The six-digit resolution of the Micro dual channel counter / rate meter is ideal for comparison of rates that are close to each other.