Lumel N31U Universal Digital Panel Meter, 96 x 48 mm

The Lumel N31U is a 96 x 48 mm digital panel meter with a multi-purpose input. One unit reads Pt100 and Pt1000 sensors, six thermocouple types, resistance, a potentiometer, millivolt signals from shunts, 0 to 10 V and 0/4 to 20 mA, so the same part number covers most local indication jobs in a process plant. It has one alarm relay, an RS-485 Modbus port and a wide a.c./d.c. supply, and it can power a two- or three-wire transmitter from its auxiliary output.

One meter for many process signals

Plants usually need to show a temperature, a pressure or a level on the front of a panel, and the signal type differs from loop to loop. The N31U handles that with a single model: the input type is chosen in the menu, the unit is selected from 56 variants (degrees, bar, kg/h, m3/h, kWh and others), and a 32-point individual characteristic with mathematical conversions (square root, x squared, 1/x) lets it linearise tank levels, flow signals from differential pressure or any other non-linear sensor. The top line can show the measured value while the bottom line shows the unscaled input signal or the time.

Key features from the data sheet

• Universal input: temperature sensors, resistance, standard signals and potentiometer.
• Supply of external transducers from the meter (24 V d.c. / 24 mA auxiliary supply).
• One alarm output with LED signalling in seven modes, with threshold and delay for both switching on and off.
• Minimum and maximum value memory, programmable averaging and a walking-window algorithm.
• RS-485 MODBUS RTU, configuration from the keys or with the free eCon software.
• Real-time clock with automatic summer and winter time change, password protection and IP65 front.

Technical specification

Input types and ranges (nominal range)

Outputs, interface and construction

Ordering and selection

The ordering code is simply N31U for the standard Polish-English version with 40 to 253 V a.c. or 20 to 300 V d.c. supply, one relay output and RS-485, without extra quality requirements. Adding the digit 2 as the acceptance-test option gives an extra paid calibration certificate. Custom versions need agreement with Lumel. The sister models N30U and N32U in the same range cover simpler and larger variants; the N31U is the one to quote when a single alarm and a universal input are needed.

Installation notes from the manual

Cut a 92 x 45 mm slot, fit the meter from the front with the connector strips removed, and wire terminals 1 to 10 (inputs) with up to 1.5 mm2 and terminals 11 to 18 with up to 2.5 mm2. Connecting the supply to terminals 16 to 18 together damages the meter, so use the pair that matches the supply voltage. Factory Modbus settings are address 1 and 9.6 kbit/s, and the default input type is 10 V, so choose the sensor type before commissioning. Measuring inputs and the auxiliary supply share one potential.

Where it is used in GCC plants

The N31U fits local temperature indication on furnaces, oil heaters and compressor skids, tank level and pressure displays on 4 to 20 mA loops, and battery or shunt readouts, always in a protected panel. With a rated ambient up to 60 degrees C it handles hot control rooms, but panels in direct sun should be checked.

Frequently asked questions

Which temperature sensors does the N31U accept?

Pt100, Pt1000 and thermocouple types E, J, K, N, R and S, with reference-junction compensation.

Can it power a 4 to 20 mA transmitter?

Yes, it has a 24 V d.c. auxiliary supply output for two- and three-wire transmitters.

How many alarm outputs are there?

One relay output, configurable in seven alarm modes.

What is the panel cut-out size?

92 x 45 mm, for a 96 x 48 mm front.

Can I linearise a non-linear signal?

Yes, with a 32-point individual characteristic or mathematical functions such as square root and x squared.

Related Lumel products: Lumel ND20 221100M1 Power Network Meter, RS-485, Lumel N32H 130000000M0 Digital DC Circuit Meter, Lumel N14 3-Phase Power Network Meter with RS-485, Lumel N43 11100M0 DIN-Rail 3-Phase Power Network Meter, Lumel RE82 131100M0 PID Temperature Controller, 48 x 96 mm and Lumel NF20 Power Factor Controller, 4 to 12 Steps.

Documents and quotation

Ask us about the N31U from Lumel: we are an independent supplier in Muscat and prepare quotations on request only. The Lumel N31U user manual is attached. The data sheet N31U-19 supplies the input table and ordering example used here. Your engineer should review the maker documents before an order is placed. Further products: Temperature Instrumentation.