Panel Meter for Frequency, Rate, or Period Applications

Frequency, Rate & Period Panel Meter Frequently Asked Questions

What frequency range can Channel A and Channel B each measure?

Channel A measures from 0.005 Hz to 1 MHz. Channel B measures from 0.005 Hz to 250 kHz — the two channels aren't identical in maximum frequency, so when wiring a high-frequency signal, it should generally be connected to Channel A.

How does this meter achieve fast, accurate readings at low frequencies compared to a conventional pulse counter?

It uses an inverse-period technique — timing an integral number of periods over the gate time and calculating frequency as the inverse of that period — rather than simply counting pulses within a fixed window. This gives both greater accuracy and faster update response, particularly at low frequencies where conventional pulse counting is slow and imprecise.

What is gate time, and what range can it be set to?

Gate time is the measurement window the meter uses when timing periods, selectable from 10 ms to 199.99 seconds. A longer gate time improves stability and reduces reading variation on a noisy signal, at the cost of slower update response.

What input signal types does this meter accept?

NPN or PNP proximity switches, TTL or CMOS logic, magnetic pickups, contact closures, low-level turbine flow meter outputs down to 12 mV, and AC line inputs up to 250 Vac — all on the same FR signal conditioner board.

Does the meter need external power to run a proximity switch or sensor?

Not necessarily. A built-in isolated excitation supply — 5, 10, 12, or 24 Vdc, jumper-selectable — can power proximity switches and similar sensors directly, removing the need for a separate power supply for the sensor.

What's the difference between the standard counter and the Extended counter version?

The standard version displays frequency, rate, or period from each channel independently. The Extended version adds simultaneous rate-and-total display, up/down counting, totalizing with external inhibit, custom curve linearization (up to 180 points), and arithmetic functions between the two channels (A+B, A-B, AxB, A/B, A/B-1).

How does the A/B ratio function help with ingredient mixing applications?

A/B calculates the ratio between the two channel readings, so if Channel A and Channel B are scaled to two ingredient flow rates, the meter can display and alarm on the actual mixing ratio in real time — letting an operator add more of ingredient B until the target A/B ratio is reached.

Can noise on the input signal be filtered without slowing down the meter's response to real changes?

Yes. The adaptive digital filter is specifically designed to reduce variation from noise while still responding quickly to genuine signal changes, as opposed to a fixed averaging filter that would smooth out both noise and real changes equally.

How accurate and stable is the meter's internal time base?

The crystal time base is calibrated to ±2 ppm, with a span temperature coefficient of ±1 ppm/°C and long-term drift of only ±5 ppm/year — which is why frequency measurements from this meter are accurate enough for applications like precise AC line frequency monitoring.

Can this meter linearize a turbine flow meter that's inaccurate at low flow rates?

Yes, on the Extended version. Custom curve linearization using up to 180 user-entered data points, spline-fit and downloaded to the meter, is specifically useful for correcting the non-linear low-end response common to turbine flow meters, extending their accurate dynamic range.

Frequency, Rate & Period Panel Meter Questions From the Field

Why is my meter counting more pulses than the known speed of the machine would suggest?

This is a frequently reported issue, and it's commonly traced to electrical noise being interpreted as extra pulses rather than a wiring or programming fault. Selecting a tighter noise filter setting (250 Hz or 30 kHz instead of 1 MHz, if the actual signal frequency allows it), increasing contact debounce time for a mechanical switch input, or enabling the adaptive digital filter are the standard first troubleshooting steps.

My reading is erratic on a mechanical limit switch or relay contact input — could debounce settings be the cause?

Yes, this is a well-documented cause. A mechanical contact physically bounces for a few milliseconds when it closes, and without adequate debounce filtering, those bounces can be counted as multiple separate pulses. Selecting the 3 ms or 50 ms debounce setting (rather than 0 ms) for mechanical contact inputs typically resolves erratic counting from this cause.

Why does my Channel B input not register a high-frequency signal that works fine on Channel A?

Channel B is rated to a lower maximum frequency (250 kHz) than Channel A (1 MHz), so a signal above 250 kHz simply won't register correctly on Channel B even if it reads correctly on Channel A. Confirming which channel a given signal's frequency is actually compatible with, rather than assuming both channels are identical, resolves this.

Why does my rate reading lag noticeably behind an actual speed change?

This is typically a gate time and filtering tradeoff rather than a fault — a longer gate time or a longer adaptive filter time constant improves reading stability but adds lag before the display catches up to a genuine change. If fast response matters more than smoothing for a given application, shortening the gate time or filter time constant will improve responsiveness at the cost of some added jitter.

Why does my total from the totalizer not match a separate reference reading, even though the rate display looks correct?

A frequently overlooked cause is the totalizing-with-external-inhibit function being active without the operator realizing it — if Channel B is configured to pause Channel A's totalizing under certain conditions, the total will legitimately stop accumulating during those periods even while the instantaneous rate continues to display normally. Confirming whether an inhibit function is configured and active is worth checking before assuming a calibration or wiring problem.

Can noise from a nearby VFD or motor drive affect this meter's frequency reading even with shielded cable?

Yes, this remains a commonly reported issue even with proper shielding, since strong electromagnetic interference can still couple onto a signal cable running near high-power switching equipment. Rerouting the signal cable further from the noise source, confirming the shield is grounded at one end only, and tightening the noise filter or debounce settings are the standard combination of remedies for this class of interference.

Why does my up/down counter only count in one direction even though I've wired Channel B for direction control?

This is generally traced to either the direction signal on Channel B not meeting the logic threshold the meter expects, or the up/down counting function simply not being enabled in the Extended meter's configuration despite the wiring being correct. Verifying the direction signal's actual voltage levels at the meter's terminals, separately from confirming up/down mode is actually enabled in setup, isolates which of the two is the real cause.

My A/B ratio reading looks reasonable most of the time but occasionally spikes to an implausible value — why?

This is commonly caused by one channel briefly dropping to zero or a very small value — since A/B is a division, even a momentary near-zero reading on the B channel (from a brief signal dropout, a slow startup, or noise) can produce a momentary, wildly large or erratic ratio result. Reviewing whether the spike coincides with a brief signal interruption on either channel, rather than assuming a persistent calibration problem, usually explains it.