LTE DIN Rail Digital Transmitter with Ethernet Communication and Analog Outputs for Duty Cycle and Pulse Width Modulation Applications

LTE Duty Cycle / PWM Transmitter Frequently Asked Questions

What's the difference between duty cycle mode and PWM mode on this transmitter?

Both modes perform the same underlying calculation — average pulse width divided by period — but duty cycle mode reports that ratio directly as a percentage, while PWM mode scales the ratio mathematically into the engineering units of whatever the signal represents, such as relative humidity.

Why is the same signal applied to both Channel A and Channel B?

Feeding the identical signal to both channels lets the transmitter use one channel to mark the start of the ON (or OFF) period and the other to mark the period boundary, which is how it derives both the pulse width and the total period needed to calculate the t/P ratio.

How do I choose between ON duty cycle and OFF duty cycle?

Selecting leading or falling pulse edges as the measurement trigger determines which state — ON or OFF — the transmitter times and reports as duty cycle; the choice depends on which state's proportion of the period is meaningful for the application.

What does the gate time setting actually control?

Gate time, selectable from 10 ms to 199.99 s, sets how many periods are averaged together before a reading is output; a longer gate time smooths out cycle-to-cycle variation at the cost of a slower update rate.

Why does accuracy change with input frequency?

Accuracy of 0.01% holds from 0.005 Hz up to 500 Hz, loosening to 0.1% at 5 kHz and 1% at 10 kHz, since gate-time-averaged timing measurements naturally have less margin for precision as more cycles are packed into the same measurement window at higher frequencies.

What signal types can feed the A/B inputs?

The signal conditioner accepts AC signals up to 250 Vac and inputs as low as 12 mV, along with NPN or PNP proximity switch outputs, TTL/CMOS logic levels, contact closures, and magnetic pickups — jumper selections adjust the input stage to match whichever type is connected.

Do I need a separate power supply for my proximity switch or sensor?

Not necessarily — the transmitter includes a built-in isolated 5, 10, or 24 Vdc excitation output (jumper selectable) that can power a connected proximity switch or sensor directly, without a separate supply.

Does the resolution setting (1%, 0.1%, 0.01%) affect the update rate?

Resolution and gate time are separate settings, but finer resolution generally goes hand in hand with longer gate times in practice, since more periods need to be averaged to resolve smaller differences in the duty cycle ratio reliably.

Can this transmitter output both an analog signal and Ethernet data at once?

Yes — the isolated 4-20 mA (or 0-20 mA / 0-10V) analog output and the Ethernet-based Modbus TCP digital data are both available from the same duty cycle or PWM measurement.

Is this the same hardware used for the transmitter's other pulse-input measurement modes?

Yes — duty cycle and PWM measurement run on the same Extended main board and dual-channel FR signal conditioner used across the transmitter's other pulse-input applications, with the measurement mode set through configuration rather than different hardware.

LTE Duty Cycle / PWM Transmitter Questions From the Field

My duty cycle reading seems to jump around from cycle to cycle even though the source signal looks stable — what should I check?

Extending the gate time so more periods are averaged into each reading is the standard fix for cycle-to-cycle jitter in the displayed value; if jitter persists after lengthening the gate time, checking the source signal for noise on the edges being triggered on is the next step.

My PWM-scaled reading doesn't match the engineering units I expect — what's the likely cause?

Since PWM mode scales the same duty cycle ratio mathematically into engineering units, a mismatch usually points to the scaling parameters not matching the sensor's actual duty-cycle-to-reading relationship, rather than a fault in the underlying timing measurement.

My transmitter reports OFF duty cycle when I expected ON duty cycle — what should I check?

This points to the edge selection (leading vs. falling) being set opposite to what's needed; checking which edge is configured as the trigger against the intended measurement is the standard first step.

My readings are accurate at low frequencies but drift more at higher input frequencies — is this expected?

Yes — accuracy is specified as 0.01% up to 500 Hz but loosens to 0.1% at 5 kHz and 1% at 10 kHz, so some increase in reading variation at higher input frequencies is inherent to the measurement rather than a fault.

My proximity switch isn't triggering the transmitter reliably — what should I check?

Confirming the jumper selection matches whether the switch is NPN or PNP output type, and that the excitation voltage powering the switch is correctly selected, are the standard first checks for unreliable triggering.

My transmitter isn't showing up on the network — what should I check first?

Confirming the transmitter's IP configuration matches what the network expects, and that the physical Ethernet cable and switch port are functioning, are the standard first checks before suspecting a transmitter fault.

My analog output and my Ethernet reading show different values for the same measurement — why?

Both outputs are derived from the same underlying duty cycle calculation, so a mismatch usually points to different scaling or range settings between the analog output configuration and the digital reading, rather than two separate measurements being taken.

My Modbus TCP polling occasionally times out even though the transmitter appears connected — what's the likely cause?

Network congestion or too many devices polling the same transmitter simultaneously can cause intermittent timeouts; checking polling frequency from all connected clients and network traffic load is a common troubleshooting step.