Measurement Signal

A guide to measurement signal types for sensors & instrumentation, including explanations, applications and choice of products with analog & digital signals.

Products by Signal Type

Select a sensor or instrument by input or output signal type. Measure or transmit current, voltage, RS232, RS485, USB, solenoid relay switch and logic switch.

RS485 Serial Interface Pressure Sensors- RS485 output pressure sensors for incorporating into digital sensor networks. These sensors can be allocated a unique device address and connected in series to other sensors with RS-485 serial interfaces on the same communications link.
0-5 Volts Output Pressure Transducers- 0 to 5 volts output pressure transducers with amplified signal conditioning electronics and 3 or 4 wire configuration for generating a 0-5Vdc analog signal which corresponds to a specified pressure range.
0-10 Volts Output Pressure Transducers- 0 to 10 volts output pressure transducers with amplified signal conditioning electronics and 3 or 4 wire configuration for generating a 0-10Vdc analog signal which corresponds to a specified pressure range.
RS232 Serial Interface Pressure Sensors- RS232 compatible pressure transducers for linking to PC computer serial ports which are provided with communications protocol commands for handshaking and retrieving sensor data, or a RS232 interface converter with a software program with features required for displaying, recording and analysing pressure readings.
4-20mA Output Hydrostatic Level Transmitters & Sensors- Liquid level transmitters with a 4 to 20 milliamp current loop output signal for determining liquid depth or the fluid level by measuring the hydrostatic pressure.
Modbus Communications Protocol Pressure Sensors- Pressure sensors with Modbus communications protocol for connecting to a serial bus or a digital sensor network.
Ratiometric 0.5-4.5 Volts Output Pressure Transducers- Ratiometric voltage output pressure transducer with a 0.5 to 4.5 volt signal which is proportional to the nominal input supply voltage of 5 volt dc.
1-5 Volts Output Pressure Transducers- 1 to 5 volts dc output signal pressure transducers with a 4 volt output span proportional to the specified pressure range, with a 1Vdc output signal at the lowest input pressure and 5Vdc output signal at the highest input pressure.
HART Pressure Transmitters- HART pressure transmitters for configuration via a distributed control system (DCS) or HART communicator.
0-20mA Output Pressure Transmitters- 0 to 20 milliamp output pressure transmitters with a 3-wire configuration for installations where the positive voltage supply is separated from the current loop signal wires.
0-10 Volts Output Hydrostatic Sensors, Probes & Transducers- Analog output hydrostatic sensors with a 0 to 10 volt amplified output signal for measuring liquid head pressure or fluid level.

Analogue Measurement Signal

Measurement sensors & instrumentation which have an analog signal input or output.

4-20mA

Instrumentation for measuring, sending or converting a 4 to 20 mA current loop signal

0-20mA

Instrumentation for measuring, sending or converting a 0 to 20 mA current signal

0-10Vdc

Instrumentation for measuring, sending or converting a 0 to 10 volts dc analogue signal

0-5Vdc

Instrumentation for measuring, sending or converting a 0 to 5 volts dc analogue signal

1-5Vdc

Instrumentation for measuring, sending or converting a 1 to 5 volts dc analogue signal

0.5-4.5Vdc ratiometric

Instrumentation for measuring, sending or converting a ratiometric 0.5 to 4.5 volts dc analogue signal

mV/V strain gauge/ ratiometric

Devices with a wheatstone bridge strain gauge circuit input/output for low voltage mV signal without any amplification. Select a device with a output sensitivity that is proportional to the input supply voltage.

Digital Interface Measurement Signal

Measurement sensors & instruments which have a digital interface.

USB

Instrumentation with a universal serial bus (USB) digital connection for use with PC computers.

RS485

Instruments with RS485 serial coms for linking to digital electronics or with multiple RS485 serial devices.

RS232

Instrumentation with RS232 digital communications for connecting to industrial computers, desktop PC and other microprocessor equipment with serial bus interface cards.

SDI-12

Instrumentation with a serial data interface with a baud rate of 1200 for connecting to environmental data acquisition (EDA) products.

Modbus

Instrumentation which uses the Modbus serial communications protocol.

I²C

Instrumentation that has a I²C (Inter-Integrated Circuit) serial computer bus interface for inter-connection & compatibility with other I²C components.

DCT 532 I²C Pressure Sensor for TWI Communication

Help Guides

Question & Answers

Find answers to questions about analogue and digital measurement signals used to transmit readings from measurement instrumentation.

Analogue vs digital signal usage

Do most sensors have an analogue output?

Yes and no, but typically all sensors start with an analogue signal of some kind , the transducer but normally its too weak a signal to transmit far and is uncompensated for environmental changes. A signal conditioning unit (SCU) compensates and converts the signal to something more universal like RS485, 4-20mA, 0-10Vdc , Modbus, IO-Link, or i2c.

Analogue is still dominant on long cables of say 20-100m, but digital is becoming much more common inside instrumentation and packages, and digital interfaces such as RS485 can be used over much greater distances without data corruption. Sensors on production road vehicles for instance, are becoming all digital, typically use the CANbus digital protocol.

Is 0.5-4.5Vdc output proportional to input supply voltage

Many other companies use “Ratiometric” to describe a pressure transducer with a “0.5 to 4.5 Vdc” output signal. Does it really mean that the output signal is proportional to the input supply and why is it not specified as a sensitivity in mV/V?

mV/V senstivity is used to describe the output of a strain gauge output type device, e.g. 2mV/V, the output is typically much smaller than the input voltage hence the Millivolt to Volts ratio. 0.5 to 4.5 V output is an amplified output where the output is comparable to the input voltage which is typically 5Vdc.

Also on some circuits there is a limitation on the supply voltage e.g. 5V +/-0.5V, and a mV/V description of the output is more suited to describing outputs that can be used with a wide range of supply voltages. However a change in input voltage within those limits of constraint will directly affect the output hence the term “ratiometric”, whereas an input supply that is regulated will maintain a constant output.