The Micro dual-channel frequency, rate and period meter is a basic operating mode of the Micro counter with the FR signal conditioner board. It can display frequency from 0.005 Hz to 1 MHz, rate in engineering units, and period (inverse of frequency). The normal displayed value can range up to 999,999 counts. Above that level, the display will flash and go into four-digit XXXXEX scientific notation. Square root extraction is standard. Each channel (A or B) may be independently scaled for frequency, rate or period. The displayed channel is selected via a front panel pushbutton.
Examples of applications are the accurate display of AC line frequency, RPM, speed from proximity switch inputs, and flow from turbine flowmeter inputs.
Fast, High Resolution Measurement
The Micro frequency / rate meter determines frequency by timing an integral number of periods over a specified gate time, and then taking the inverse of period. Rate is obtained by multiplying the input by a scale factor. The inverse period approach allows greater accuracy and faster update times than conventional meters which count signal pulses over a specified time interval. AC line frequency may be accurately measured to 50.0000 or 60.0000 Hz in a few line cycles. 1000 Hz signals may be measured to 0.01 Hz resolution at up to 25 readings per second. Fast response is ideal for alarm and control applications.
To reduce the effects of signal noise, a count by 10 or 100 feature with rounding is selectable. Variations in the displayed reading can also be reduced by selecting a longer gate time. An adaptive filter can reduce variations due to noise while rapidly responding to actual changes in the signal.
Extended Counter Capabilities
An Extended counter version provides capabilities beyond those of the standard counter:
Rate and total simultaneously. One channel can display total while the other displays rate. The selection for either channel is via a front panel pushbutton. This mode is ideal for flow applications when the same signal is applied to both channels.
Custom curve linearization. Exceptionally accurate custom curve linearization allows linearization of the low end of turbine flowmeters. For setup, up to 240 data points can be input into a spreadsheet or text file by the user. The computer then calculates nonlinear segments, which are downloaded into the meter via RS232. The Extended version allows linearized rates to be totalized.
Arithmetic functions. The Extended counter makes arithmetic functions available, namely A+B, A-B, A*B, A/B and A/B-1 (draw). For example, A+B allows two input flows to be summed for total flow, while A-B allows outflow to be subtracted from inflow for net flow. If transducers with a frequency output are used, A*B allows horsepower to be displayed based measured torque and RPM, or based on force and velocity. A/B can be used for the proper mixing of ingredients, while A/B-1 (draw) is used to compare rates for stretching or tensioning.
Universal Signal Conditioner
The 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.
A built-in isolated 5, 10, or 24 Vdc excitation supply can power proximity switches and other sensors, thus eliminating the need for an external power supply.
Micro Series instruments can be powered from 95-240 Vac ±10% and 95-370 Vdc, or optionally from 12-34 Vac and 10-48 Vdc. Any setup functions and front panel keys may be locked out for simplified usage and security. The popular 1/8 DIN version with 0.56″ high digits is environmentally sealed to NEMA-4X (IP65) from the front when panel mounted, and is available with red or green LEDs.
6 digits, 7-segment
Available with 0.56" or 5.0" digits.
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,
-1.15 V to +1.15 V, +1.25 V to +2.1 V, -2.1 V to -1.25 V
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
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
AC Line Frequency
The Micro frequency meter will accept line voltages up to 250 Vac and display line frequency to 6-digit accuracy (50.0000 or 60.0000) in a few line cycles. Fast low frequency response is achieved by timing the period and taking its inverse.
RPM and Speed
The Micro frequency meter can sense the low-level signals from magnetic pickups or the NPN or PNP transistor output of active sensors. These can be powered directly by the meter. Display in RPM in tachometer mode or rate in units of speed is achieved by mathematically scaling the meter.
Flow Rate and Simultaneous Total
The Micro frequency / rate meter is compatible with all flow meters which generate pulses at a frequency proportional to flow rate. The Extended version can display scaled rate or total for the same input at the push of a button, and alarm from both the rate and total. The Extended version can also linearize flow transducers so as to extend their dynamic range.
Combining Two Rates
In a repetitive fill operation (as illustrated by example), a setpoint offset of -50 will allow a shutoff setpoint to be set for 1000 and actual shutoff to occur at 950 if it is known that 50 units will still flow following shutoff. An offset can also be applied to emptying operations.
Custom Curve Linearization
The Extended Micro frequency / rate meter can linearize the output turbine flow meters, which tend to be nonlinear on the low end. Linearizing improves the dynamic range and accuracy of turbine flow meters.
The Micro dual channel rate meter can independently scale, display and alarm two pulse input channels. All signal or alarm data can further be transmitted via RS232 or RS485, including peak readings and arithmetic combinations of the two rates. The displayed rates can also be transmitted as an isolated 4-20 mA analog output.