Calibration of measurement and vibration analysis systems, like other precision instruments, is a critical requirement in manufacturing plants. In factories, vibration monitoring is typically performed for two main purposes: protection and condition monitoring. In protective systems, the continued operation of machinery depends on the measured vibrations being below acceptable limits. Therefore, inaccuracies in vibration measurement can unnecessarily lead to production halts or, conversely, result in catastrophic damages. In condition monitoring systems, with slightly lower importance, a lack of calibration in the measurement system can lead to misjudgments regarding the machine’s condition, incorrect troubleshooting, and consequently impose significant costs on the factory.

Tavator Sepahan Engineering Company provides calibration services for various non-contact and contact sensors, as well as vibration meters and different analyzers, using various equipment including calibrators, shakers, controllers, oscilloscopes, and analyzers. These tests include:

Laboratory Calibration:
Calibration of body sensors (accelerometers and velocity sensors)
Calibration of proximity sensors: static behavior testing and dynamic behavior testing
On-Site Calibration:
Calibration services for measurement and vibration analysis systems.

Calibration of Body Sensors

Calibration of body sensors, which includes accelerometers and velocity sensors, is carried out using a shaker and vibration controller. In this test, the frequency response of the sensor is measured for the intended operating frequency range. Typically, these types of sensors do not allow for sensitivity adjustment, meaning that they cannot be calibrated for their defined sensitivity. However, their sensitivity can be measured at different frequencies. The result of the test indicates whether the sensor is acceptable or unacceptable. Additionally, the sensitivity of the sensor is measured and displayed at various frequencies.

Testing Methods

The best method for measuring the sensitivity of these sensors is to install them back-to-back with a designated calibration sensor and use a separate controller, shaker, and analyzer. If a specific calibration sensor is not available, a reliable alternative is to use a measurement from another sensor and a vibrometer.

In another method, the reference vibration is measured by the shaker itself, and the output should be measured with a monitor or voltmeter. This method can also be performed on-site and does not require any additional equipment.

Typically, these calibrators have the capability to connect to a computer and can automatically provide confirmation of the calibration results.

Calibration of Non-Contact Sensors – Proximity Sensors

Since proximity sensors provide both DC and AC outputs, the calibration of these sensors includes two parts: static and dynamic testing. The installation of these types of sensors must be done with greater precision compared to contact sensors.

In the static test, the DC output of the sensor is recorded at various distances of the sensor tip from the target (substituting for the shaft) using a voltmeter, and the sensitivity curve of the sensor is plotted and calculated based on these values.
In this plot, the nonlinear regions at both the lower and upper ends of the sensor are also identified.
In the dynamic test, the AC output of the sensor is measured using a vibrometer for the sinusoidal movement of the target plate (substituting for the shaft) at a predetermined amplitude and compared with the original value.
The calibrator for these sensors is commonly known as the TK3 device.

On-Site Calibration – Loop Check

In a warm loop check, the vibration measurement systems of the sensors are disconnected from their installation location and attached to a shaker (for body sensors) or to the TK3 (for proximity sensors). By creating vibrations with a specific frequency and amplitude, the desired value must be read on the control room monitor and compared with the shaker value. Typically, a discrepancy of up to 2% is considered acceptable.