LT DIN Rail Analog Transmitter with Serial Data Communication and Analog output for DC Voltage and Current Input Signal Applications

DC Voltage and Current Input Transmitter Frequently Asked Questions

What's the difference between the transmitter's DC voltmeter mode and DC ammeter mode?

Voltmeter mode measures a voltage signal directly across the input terminals, while ammeter mode measures current flowing through the input circuit. The two modes are jumper-selected rather than both active at once, so the transmitter is configured for whichever signal type the application produces.

Why are the input ranges jumper-selected instead of software-selected?

Jumpers physically reconfigure the signal-conditioning hardware path for a given range, keeping the analog front end matched to the expected signal level for best accuracy. Once the jumpers are set for the intended range, scaling, output type, and filtering are handled in software.

Why do the two lowest voltage ranges get 1 GΩ input impedance while the others don't?

Low-level millivolt and low-volt sources are typically higher-impedance and more easily loaded down by a measuring instrument's own input resistance, so the extra-high impedance on the ±200.00 mV and ±2.0000V ranges specifically protects accuracy where loading effects matter most.

Why does the 5A current range use a built-in shunt instead of a direct sensing input?

At 5A, measuring the voltage drop across a built-in 10 milliohm shunt produces a small but measurable voltage the transmitter's existing voltage-sensing circuitry can read, extending accurate measurement to higher current levels without separate high-current-rated electronics.

What does "isolated" mean for the analog and serial outputs?

Isolated means the output circuitry has no direct electrical connection to the input signal or to the transmitter's power ground, which prevents ground loops between the transmitter and whatever device it feeds.

How is this different from an LTE Series transmitter?

The LT Series communicates over RS232 or RS485 serial data, while the LTE Series connects directly via Ethernet. Both share the same signal-conditioning boards and core measurement performance; the choice comes down to whether the installation is wired for serial daisy-chaining or a LAN.

Can the custom curve linearization be applied to current inputs, or only voltage inputs?

It applies to whichever range and signal type the transmitter is configured for — a common example is using a 4-20 mA current input to calculate tank volume or flow rate through the 180-point spline-fit approach.

Does the overcurrent protection rating mean the transmitter can run continuously at that elevated level?

No — the overcurrent protection multipliers (such as 25x for the 2 mA range) describe tolerance for a fault or transient condition without damage, not a rating for safe continuous operation; normal operation is expected to stay within the range's specified full-scale rating.

Can the transmitter power an external sensor directly?

Yes, through its selectable excitation output (5V, 10V, 12V, or 24V DC), meant to power transducers or two-wire devices that need an excitation supply rather than requiring a separate power source.

What happens if I need a different signal type than DC voltage or current?

The transmitter supports several interchangeable signal conditioner boards (AC RMS, process/ratiometric, load cell, thermocouple, RTD, resistance, and frequency inputs, among others), so a different input type is typically a board swap rather than a different product line.

DC Voltage and Current Input Transmitter Questions From the Field

My analog output isn't moving even though the input signal is clearly changing — what should I check first?

Confirm the output type configured in software (4-20 mA, 0-20 mA, 0-10V, or -10 to +10V) actually matches what the receiving device is wired to expect and measure. A common cause is the output set correctly at the transmitter but the receiving PLC card configured for a different range.

The reading doesn't match what I measure with a handheld meter at the input terminals — why?

This almost always traces to a scaling or range mismatch rather than a hardware fault: if the jumpers are set for one range but the setup software's scaling assumes a different one, the transmitter converts accurately but displays or outputs the wrong value.

Why would a 5A shunt-based reading drift more than the lower current ranges?

Because the 5A range is measured indirectly through the shunt's IR drop, it's specified with a flat ±10 mA accuracy rather than the tighter percentage-based accuracy of the other ranges, so a small amount of extra variation on this range is expected, not necessarily a fault.

My RS485 daisy-chain has multiple transmitters, and one of them isn't responding — where do I start?

Confirming that transmitter's address is unique and correctly set is the typical first step, since an address conflict is one of the most common reasons a single unit goes silent while the rest of the chain communicates normally.

I'm seeing noise or instability in a low-level millivolt reading — is that likely a transmitter problem?

Not necessarily. Low-level voltage inputs are the most susceptible to picking up external electrical noise on the wiring itself, so checking cable shielding, grounding, and routing away from noisy power conductors is typically the first step.

Why does my reading jump or reset unexpectedly when I switch input ranges?

Changing the input range via jumpers is a hardware-level change, and the software scaling and calibration reference need to be re-checked to match the newly selected range; an unexpected jump after a jumper change usually means the software side wasn't updated to match.

Can two transmitters set to the same nominal range read slightly differently for the same physical input?

Small unit-to-unit differences can occur since each unit's factory calibration is specific to its own signal conditioner board. If the difference exceeds the specified tolerance, verifying both units against a known reference source is the standard field step.

The excitation output voltage seems lower than expected under load — is that normal?

Each excitation setting has a rated maximum current; if the connected sensor draws more current than that rating, the output voltage can sag. Checking the actual current draw against the rated capacity is the usual first diagnostic step.