LT DIN Rail Analog Transmitters with Serial Data Communication and Analog outputs for Scale and Weighing Applications P/N LT20P

Scale & Weighing DIN Rail Transmitter Frequently Asked Questions

Why would someone choose the DC signal conditioner board over the dedicated load cell board for a weighing application?

Documented specification specifically frames the DC board as usable "in lieu of" the load cell board when set to ratiometric operation — while the load cell board offers more sensitive ranges (±20/±50 mV at 1 µV resolution versus the DC board's ±200 mV at 10 µV resolution), an application whose sensor signal naturally falls in the DC board's less sensitive range could use either board interchangeably, since both are documented as achieving the same 0.01% of full scale ±2 counts accuracy.

Does the relay setpoint offset feature change the underlying weight reading, or only when the relay physically triggers?

Only the relay trigger point — documented example specifically describes the offset as adjusting when the ON/OFF control action occurs (97.5 lbs instead of 100 lbs in the cited example), not altering the actual measured and displayed weight value itself; the displayed reading continues showing the true measured weight while the relay's trigger point is what shifts by the programmed offset.

Why does selecting the fixed right-hand dummy zero preclude using a decimal point?

Documented explanation specifically describes this mode as shifting the display to accommodate a fixed zero digit on the right side, extending the displayable range up to 999,990 — since the display has a fixed total number of digit positions, dedicating one to this fixed right-hand zero uses up the position that would otherwise hold a decimal point, which is why the two features are documented as mutually exclusive.

Does entering 0 for the auto-zero limit disable zero compensation entirely, or just reduce its sensitivity?

Entirely — documented specification specifically states entering 0 disables auto-zero, rather than setting it to a minimal but still-active tracking window; the auto-zero limit ranges from 0 (off) up to 9 counts, with 0 specifically documented as the off state rather than the narrowest active tracking range.

Between the coordinate reading method and the manual coordinate method, does one produce more accurate calibration than the other?

Not inherently — documented guidance specifically frames these as suited to different situations rather than one being more accurate: the coordinate reading method is documented as ideal when an external calibration reference is available (letting the transmitter read actual signal values directly), while the manual coordinate method is documented as suitable specifically when no external reference is available, relying instead on manually entered input values.

Can more than four 350-ohm load cells be connected to a single transmitter by using a higher-current external excitation source?

The page doesn't document this as a supported configuration — the four-cell figure is specifically tied to the transmitter's own built-in 10V, 120 mA excitation supply rating; while the concept of external excitation exists in general load cell system design, this specific transmitter's documented specification describes its own built-in supply as the basis for the four-cell parallel limit, not a higher-capacity external option.

Does the documented 0.1 µV/°C zero tempco mean auto-zero should be run on a fixed schedule, or only when temperature actually changes?

Documented guidance specifically ties the auto-zero recommendation to actual temperature change ("use auto-zero when temperature changes") rather than to a fixed time interval — since the tempco figure describes drift specifically driven by temperature, a stable-temperature environment wouldn't be expected to need auto-zero as frequently as one experiencing genuine temperature swings, making the trigger condition documented as temperature-based rather than schedule-based.

Does the count-by rounding function affect the value transmitted over the analog output and serial data, or only what's shown on the display?

Documented description specifically frames count-by as a display rounding behavior — since the transmitter's analog output and serial data are documented as tracking the underlying measured and scaled reading, the specific interaction between count-by rounding and those output channels isn't detailed as identical to the display in every configuration, making it worth confirming against the actual output value in a given setup if downstream equipment needs to match the rounded display figure exactly.

If both a relay setpoint offset and an auto-zero function are active at the same time, do they interact or interfere with each other?

Not as documented — these two features are described as addressing entirely separate concerns: relay setpoint offset shifts when a control action triggers relative to a target weight, while auto-zero compensates for small drift around the zero point when the reading rests near zero; since one operates around a nonzero setpoint and the other specifically around zero, they're documented as independent functions rather than ones that would typically conflict.

Does the transmitter's documented 0.01% of full scale accuracy apply identically whether it's paired with the load cell board or the DC signal conditioner board?

Yes — documented specification explicitly states transmitters with either board offer 0.01% of full scale ±2 counts accuracy, meaning this accuracy figure is presented as a shared specification across both board options rather than one board being documented as inherently more accurate than the other; the meaningful difference between the two boards is their sensitivity range and resolution, not this stated accuracy figure.

Zero Tracking & Auto-Zero Questions From the Field

What specifically is "zero tracking," and why do most industrial scales include it rather than requiring purely manual zeroing?

Documented explanation specifically describes zero tracking as automatically maintaining the zero indication within a defined limit, compensating for drift caused by internal offset voltage changes, component variation, and environmental factors like temperature — without it, documented guidance notes the zero point would drift noticeably as conditions change, making purely manual zeroing impractical for continuous operation.

Does zero tracking operate continuously regardless of scale activity, or only under specific documented conditions?

Only under specific conditions — documented industrial scale guidance specifically requires the scale be out of motion (commonly defined as no movement for about one second) and within a defined zero tolerance window before zero tracking is permitted to act; tracking is documented as disabled during active motion or when the reading falls outside that tolerance range.

Is there a meaningful tradeoff between setting a wider versus narrower zero tracking window?

Yes — documented guidance specifically frames this as a genuine tradeoff: a wider tracking window (more counts/divisions) gives a more stable zero point less affected by temperature drift, but a narrower window (or disabling tracking) gives more responsiveness to genuinely small applied loads at the cost of a less stable, more drift-prone zero point.

Yes, by documented design intent — documented explanation specifically describes this as a deliberate feature rather than a fault: if an added weight falls within the configured tracking window, the scale is documented as "tracking" it and treating it as zero drift rather than a real load, which is why selecting an appropriately narrow window matters for applications needing to detect small load additions.

Does formal weighing-instrument regulation (such as international recommendations for non-automatic weighing instruments) place any specific conditions on when zero tracking is permitted to operate?

Yes — documented regulatory guidance specifically describes zero tracking as permitted to operate only when the indicated value is at or near zero (or the equivalent negative net value at zero gross weight) and the instrument is in a stable, non-moving state — formal regulatory frameworks are documented as placing structured conditions on tracking operation, not leaving it as an unconstrained continuous function.

If a scale's zero tracking function can't be disabled for testing purposes, is there a documented workaround for verifying genuine zero-point accuracy?

Yes — documented field practice specifically describes deliberately applying an additional small load (commonly cited around 10 times the scale's division size) specifically to push the reading beyond the tracking window's range, allowing a technician to observe the instrument's true near-zero accuracy and zero error without the tracking function masking it.

Does frequently triggering auto-zero or tare functions carry any documented downside on instruments that log this activity to internal memory?

Yes, on at least some documented instrument families — documented guidance specifically warns that certain weight controllers save data to internal memory every time zero, tare, or auto-zero functions run, and that very frequent triggering can approach a documented finite write-cycle limit on that memory, with a risk of data corruption at power-up if that limit is reached.

Is manually zeroing the gross weight display subject to the same documented tolerance limits as automatic zero tracking?

Yes, typically — documented guidance specifically notes that a manual zero command (whether via a front-panel button or a communications port command) is commonly limited by the same configured zero tolerance parameter that governs automatic tracking, meaning an operator generally can't manually zero out a reading that falls outside the instrument's documented allowable zero range.