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

LTE Duty Cycle & PWM Transmitter Frequently Asked Questions

Why does documented accuracy degrade from 0.01% at frequencies up to 500 Hz to a full 1% at 10 kHz?

Documented specification specifically ties accuracy tiers to frequency, with the finest 0.01% figure documented across 0.005 Hz to 500 Hz, degrading to 0.1% at 5 kHz and 1% at 10 kHz — since duty cycle is computed by timing pulse width against total period using gate-time-based counting, higher-frequency signals leave proportionally less absolute time within each cycle to resolve fine timing differences, which is documented as the reason accuracy coarsens as frequency increases.

Why does the transmitter apply "the same signal" to both Channel A and Channel B for duty cycle measurement, rather than using two independent signal sources?

Documented description specifically states duty cycle measurement applies the same signal to both channels — this is consistent with the transmitter needing to independently detect both the pulse width (t) and the total period (P) from that single waveform, using the shared A/B channel architecture to extract both measurements from one signal rather than comparing two genuinely different, independent inputs the way some other LTE Series dual-channel modes do.

Does PWM mode's documented scaling to "engineering units" change the underlying accuracy of the duty cycle measurement itself?

No — documented description specifically frames PWM mode as determining the same duty cycle ratio as duty cycle mode, then mathematically scaling that ratio for display in engineering units; this scaling is a downstream mathematical conversion applied after the duty cycle ratio itself has already been measured, so the documented accuracy figures for the underlying duty cycle/PWM measurement apply the same way regardless of whether the final display is in percent or a scaled engineering unit.

Why does the documented PWM example specifically use a 120 Hz constant carrier frequency rather than an arbitrary frequency?

The page documents 120 Hz specifically as "such as" one example of a constant carrier frequency used in PWM transducer output format, without stating this as a fixed requirement — this is consistent with PWM transducers in general being documented as using some fixed carrier frequency (of which 120 Hz is one common real-world example) upon which the duty cycle is modulated to encode the measured value, rather than the transmitter itself requiring exactly 120 Hz to function.

Does selecting leading versus falling edge triggering change which physical portion of the waveform (ON time or OFF time) is measured as "duty cycle"?

Yes — documented description specifically states that by selecting leading or falling pulse edges, either ON or OFF duty cycle can be transmitted; this indicates the edge selection determines which specific portion of the periodic waveform (the ON time or the OFF time) is being measured and expressed as the duty cycle ratio, rather than edge selection being unrelated to which duty cycle value is reported.

Does this LTE Duty Cycle/PWM transmitter's documented Modbus TCP-only protocol limit compatibility compared to the RS232/RS485 LT Series duty cycle variant?

Yes — this page documents Modbus TCP specifically as the supported Ethernet Data I/O protocol at digital address 247, while the LT Series serial variant is documented elsewhere as separately supporting Modbus RTU/ASCII and Laurel Custom ASCII; a control system needing a protocol other than Modbus TCP would need to reference the LT Series serial variant rather than this LTE Ethernet variant.

Does the documented power consumption figure (2.4W typical) differ from the 2.5W typical figure documented on several other LTE Series transmitters?

Yes — this page documents 2.4W typical at 24V (4W with max excitation output), a slightly different figure from the 2.5W typical / 4.0W max figures documented on several other LTE Series pages; this genuine difference reflects that documented power consumption varies by specific transmitter model and its particular signal conditioner board, so this duty cycle/PWM transmitter's own figures shouldn't be assumed to match other LTE Series product pages.

Can the same physical transmitter be reconfigured between duty cycle mode and PWM mode, or does each require separate hardware?

Documented description presents duty cycle mode and PWM mode as two configuration options built on the same underlying Extended main board and FR signal conditioner, distinguished by whether the ratio is displayed directly as a percentage (duty cycle mode) or mathematically scaled into engineering units (PWM mode) — this is consistent with a setup/configuration choice on shared hardware rather than a distinction requiring different transmitter models.

Does the documented resolution selection (1%, 0.1%, or 0.01%) trade off against the transmitter's documented update rate?

The page documents both resolution and update rate as tied to the selectable gate time (10 ms to 199.99 s) without stating resolution and update rate are directly linked to each other independently of gate time — since finer resolution generally benefits from longer gate times to average more integral periods together, and the documented output update rate is also directly governed by gate time, selecting a longer gate time for finer resolution is consistent with correspondingly slowing the update rate, the same general gate-time tradeoff documented across the LTE Series.

Does the Extended main board requirement for this duty cycle/PWM transmitter also enable the custom curve linearization documented elsewhere for other LTE Series Extended-board transmitters?

Yes — documented features section specifically lists "Extended allows up to 180 data points for custom curve linearization and a rate derived from consecutive readings" as part of this transmitter's own feature set, consistent with the same Extended main board capability documented across other LTE Series FR-based transmitters, applicable here to further correcting or scaling the duty cycle/PWM-derived reading.

PWM Sensor Signal Conditioning Questions From the Field

Why do some humidity sensor designs specifically encode relative humidity as a duty cycle ratio rather than a simple analog voltage?

Documented sensor design examples specifically use a capacitive humidity-sensitive element as part of a timing circuit (such as connected to the threshold and trigger pins of a 555-style timer), where the sensor's own changing capacitance directly determines the charge/discharge timing and therefore the resulting duty cycle — this documented approach makes the duty cycle itself inherently proportional to humidity, and documented analysis notes this method can also make the resulting frequency independent of supply voltage when duty cycle is set near 50 percent.

Is there a documented typical accuracy figure achievable with a duty-cycle-based humidity sensing circuit?

Yes — one documented circuit design specifically cites an accuracy of less than ±3.9 percent RH using a duty-cycle-timing approach based on a variable-capacitance humidity sensor; this documented figure gives a concrete sense of the accuracy range achievable with this type of PWM/duty-cycle-encoded humidity sensing method.

Why does PWM output specifically offer better noise immunity and lower power consumption compared to a current-loop transducer output, according to documented technical analysis?

Documented technical comparison specifically notes PWM output requires less than 1mW when connected to a high-impedance node, versus 20mW to 100mW documented for a comparable current-loop transducer in a 5V system — documented analysis attributes PWM's favorable noise immunity and lower power characteristics specifically to its pulse-timing encoding method, which the source describes as suitable for transmission over longer distances similarly to current-loop signals, but with documented efficiency advantages particularly relevant for battery-powered applications.

Is there a documented standard mapping between a transducer's ratiometric analog output range and the resulting PWM duty cycle range?

Yes — one documented PWM transducer circuit specifically maps a 0.5V to 4.5V ratiometric sensor output range to a corresponding 10% to 90% duty cycle range, with the documented "offset" corresponding to 10% duty cycle and "span" corresponding to 80% duty cycle; this documented mapping illustrates a standard, defined relationship some PWM sensor circuits use between the underlying analog measurement and the resulting duty cycle output.

Does documented guidance recommend using a dedicated frequency counter with pulse-width measurement capability to properly interpret a PWM sensor's compensated output?

Yes — documented technical guidance specifically identifies a frequency counter with a pulse-width-measurement option as one appropriate instrument for measuring a PWM sensor output's pulse width during sensor compensation, alongside the alternative documented approach of interfacing the PWM output to a microcontroller and using its internal timer to calculate the interval between low-to-high and high-to-low transitions.

Does a PWM humidity or process sensor output always require conversion to a standard 0-10V or 4-20mA signal before it can drive typical industrial control equipment?

Often yes for standard industrial actuators — documented field guidance specifically notes that standard humidifier valve or damper actuators typically expect 0-10V or 4-20mA modulating signals, and specifically recommends using a PWM converter or binary output stage where connected equipment (such as some industrial ultrasonic humidifiers requiring 24V on/off staging) cannot directly accept a PWM signal, indicating PWM-to-standard-signal conversion is a genuine, documented practical requirement in many real installations.

Is there a documented distinction between the accuracy expectations for process-control humidity applications versus general comfort-control applications?

Yes — documented field guidance specifically recommends ±2% RH accuracy for process control applications, contrasted with ±5% RH accuracy documented as acceptable for general comfort applications; this documented accuracy distinction reflects that the required precision for a PWM/duty-cycle-derived humidity reading genuinely depends on the specific end-use application's tolerance requirements.

Does sensor drift affect a PWM/duty-cycle-based humidity sensor differently than it affects other sensor output types, according to documented guidance?

Documented guidance doesn't specifically single out PWM/duty-cycle sensors as uniquely prone to drift, but does specifically recommend annual recalibration per manufacturer specifications to account for sensor drift over time in humidity sensing generally; this documented recalibration practice applies to the underlying sensing element's own drift characteristics, which would similarly affect the duty cycle output regardless of whether it's ultimately read by a dedicated PWM-capable transmitter or another signal conditioning method.