From sensor to system

The calculators on this site in the order the work is done: choosing the sensor, wiring and powering it, understanding its signal, conditioning and digitising it, then bringing it into the system and proving the result.

Stage 1 of 5 · Select the sensor

Decide what the sensor must survive and how accurate it must be where you measure: the hazardous-area marking, the enclosure rating, the process connection, and what a datasheet's accuracy figure means at your reading rather than at full scale.

Pressure transmitter accuracy calculatorCombine reference accuracy, temperature effect and long-term drift into a total probable error for your calibrated range.Process connection thread identifierMeasure the outside diameter and pitch, and find the matching G, R, NPT, metric, UNF or PG thread.Ex marking decoderWhat an ATEX, IECEx or NEC hazardous-area marking means, and whether the equipment suits your zone, gas group and ignition temperature.IP rating decoderIngress protection codes explained numeral by numeral, with the test behind each one and a check against the rating you need.Sensor accuracy spec converterPut a datasheet's "±(% of reading + % FS)", tempco and stability into one number at your reading, in units, % of reading and % FS.

Stage 2 of 5 · Wire and power it

Check that the sensor gets enough voltage at the end of its cable, that cable resistance does not become part of the measurement, and that the source can carry the load: loop power, supply drop on three- and four-wire sensors, RTD leads, current transformer burden and battery life.

4–20 mA loop power calculatorCheck that a two-wire transmitter still gets enough voltage at full alarm current, with your load and cable.Sensor supply voltage drop calculatorHow much of the 24 V reaches a three- or four-wire sensor, and how far the shared 0 V shifts its voltage output.Current transformer burden calculatorAdd up the cable and the meters on a CT secondary and compare the total with the rated burden.Battery life calculatorHow long a battery-powered sensor lasts when it sleeps, measures and transmits once per interval.RTD lead-wire error calculatorHow much cable resistance adds to a PT100 or PT1000 reading with 2-, 3- or 4-wire connection.

Copper wire resistance table (AWG and mm²)

Stage 3 of 5 · Understand its signal

Turn the physical quantity into what the sensor delivers and back: resistance of an RTD or thermistor, thermocouple voltage, bridge output in mV/V, hydrostatic pressure of a level, humidity and vibration quantities, pressure units.

PT100 / PT1000 calculatorPlatinum RTD resistance and temperature per IEC 60751. Type in either field.Thermocouple calculatorTemperature and meter voltage per NIST ITS-90, with cold-junction compensation. Type in either field.NTC thermistor calculatorBeta model from datasheet values, plus Steinhart–Hart from three calibration points.Load cell output calculatorBridge signal for one cell or several in parallel through a junction box.Strain gauge bridge calculatorOutput of a strain-gauge Wheatstone bridge for a given strain, or the strain behind a measured output. Type in either field.Pressure unit converterType in any unit; all the others update.Level to pressure calculatorHydrostatic pressure of a liquid column, and the range to calibrate a level transmitter to.Dew point and humidity calculatorDew point, absolute humidity and mixing ratio from temperature and relative humidity, or the other way round.Flow rate converterVolume and mass flow in every common unit, and flow against differential pressure on an orifice or other DP flowmeter.Vibration converterAcceleration, velocity and displacement of a sinusoidal vibration in peak, RMS and peak-to-peak, with the severity zone.

Stage 4 of 5 · Condition and digitise

Make the signal readable for the electronics: divider and gain resistors, the anti-aliasing filter, a current shunt, the ADC's resolution in the measured unit, 4–20 mA scaling and pulse outputs against the counter input.

4–20 mA converterScale a loop current to a process value and back, and check it against NAMUR NE 43.Pulse output calculatorFrequency and resolution of a pulse output, from a flow meter's K-factor or an encoder's pulses per revolution, against your counter input.ADC resolution calculatorHow fine a sensor signal is resolved by an analogue-to-digital converter, in the unit you measure.Anti-aliasing RC filter calculatorCheck an RC input filter against the ADC: corner frequency, attenuation at half the sample rate, settling to ½ LSB and delay.Instrumentation amplifier gain calculatorPick the gain resistor for a bridge or sensor amplifier and check that the output stays inside the rails.Current shunt resistor calculatorVoltage, dissipation and error of a current shunt, and the gain and resolution it needs ahead of an ADC.NTC voltage divider calculatorSize the series resistor for an NTC read by an ADC: output, sensitivity, resolution per code and self-heating over your range.

4–20 mA scaling tables

Stage 5 of 5 · Integrate and verify

Bring the value into the controller and prove what it is worth: decode Modbus registers in the right byte order, then add up every error in the chain into a total that can go into a report.

Modbus register decoderTurn raw holding or input registers into the number they carry, in every byte and word order, or a value into registers.Temperature measurement error calculatorThe whole chain in one number: sensor tolerance class, wiring or cold junction, transmitter and output, combined as total probable error and worst case.