Calibration Instruments

Calibration instruments use electrical signals or physical quantities to calibrate sensors and meters. Devices that produce electrical signals can serve as precise meters for sensor calibration, or send output signals to other devices. Common calibration signals include AC voltage, DC voltage, AC current, and DC current. Calibration instruments that produce a pulse stream, pulse range, or frequency range are also available. Signal and waveform generators are designed to produce a sine wave, square wave, triangular wave, or other predefined waveform. Most manufacturers specify calibration instruments with a range of signal values that includes minimum and maximum amounts. Devices that produce physical quantities are often traceable to national to international standards from the National Institute of Standards and Technology (NIST), Physikalisch-Technische of Bundesanstalt (PTP), National Measurement Accreditation Services of the U.K. (NAMAS), or Bureau Nationale Metrologie of France (BNM). 

Selecting calibration instruments requires an analysis of physical, electrical, process, environmental, and thermodynamic properties. Physical properties indicate whether instruments can be used to calibrate devices that sense or measure acceleration, vibration, acoustics, displacement, position, force, load, or torque. Electrical properties indicate whether calibration instruments can be used to calibrate devices that sense or measure attenuation, capacitance, charge, inductance, power, resistance or impedance. Calibration instruments that sense and measure process, environmental and thermodynamic properties are used with many variables. Examples include conductivity, liquid flow, gas concentration, humidity, moisture content, dew point, oxygen reduction potential (ORP), potential hydrogen (pH), and resistivity. Specialized products are used to calibrate resistance temperature detectors (RTD), thermistors, and thermocouples.

There are several form factors for calibration instruments. Handheld devices are designed to be operated manually, while held in one hand. Portable devices are not necessarily hand held, but may include wheels, handles, or a carrying case for ease of movement. Fixed instruments are designed to be mounted and/or used in one place. Both benchtop and panel-mounted devices are included in this category. Modular calibration instruments can be interfaced to different sensors or input ranges. Some devices use batteries for full operation, not just backup. Others require the use of a modem or RF transmitter.

Calibration instruments provide many different user interface options. Analog displays consist of a meter or simple visual indicator such as a needle or light emitting diode (LED). Analog front panels provide user inputs such as potentiometers, dials, and switches. Digital devices display numeric values and can be setup or programmed with a digital keypad or menus. Calibration instruments that use cathode ray tubes (CRT), liquid crystal displays (LCD), or other multi-line displays are also available. Some calibration instruments can be controlled or monitored via a computer interface. Others provide integral application software. Common serial interfaces include RS232, RS485, and universal serial bus (USB). Popular parallel interfaces include the general-purpose interface bus (GPIB), a standard also known as IEEE 488.

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Part Numbers for Calibration Instruments