German GTM sensor GTM model GTM price

GTM sensors are sensors that can sense temperature and convert it into a usable output signal. Temperature sensors are the core component of temperature measuring instruments and come in many varieties. According to the measurement method, they can be divided into two major categories: contact and non-contact. According to sensor material and electronic component characteristics, they are divided into resistance thermometers and thermocouples. Valve GTM sensor structure

It consists of two parts: the scale grating and the grating readhead. The figure on the right shows the structure of the linear encoder. The key component of the grating detection device is the grating readhead, which comprises a light source, condensing lens, index grating, photoelectric elements, and an adjustment mechanism. There are many structural forms of grating readheads. Based on the structural characteristics of the readhead and the application scenarios, they are classified into direct-receiving readheads (also known as silicon photovoltaic cell readheads, mirror-image readheads, beam-splitter readheads, and metal grating reflective readheads).

GTM sensor principle

The essence of a grating displacement sensor is to use the grating pitch as a standard ruler for measurement. High-resolution linear encoders are generally expensive and difficult to manufacture. To improve system resolution, Moiré fringes need to be subdivided; grating sensor systems mostly adopt electronic subdivision methods. When two gratings overlap with a slight inclination angle, Moiré fringes are generated in the direction roughly perpendicular to the grating lines. As the grating moves, the Moiré fringes also move up and down. This converts the measurement of the grating pitch into the measurement of the number of Moiré fringes. Within one Moiré fringe width, placing 4 photoelectric devices at certain intervals can achieve electronic subdivision and direction judgment functions. For example, for a linear encoder with 50 line pairs/mm, its grating pitch is 0.02mm. If four-fold subdivision is adopted, counting pulses with a resolution of 5μm can be obtained, which has reached a very high precision in general industrial measurement and control. Since displacement is a vector, both its magnitude and direction must be detected, so at least two photoelectric signals with different phases are required. To eliminate common-mode interference, DC components, and even harmonics, differential amplifiers composed of low-drift operational amplifiers are usually used. The 4 photoelectric signals obtained from 4 photosensitive devices are sent to the input terminals of 2 differential amplifiers respectively. The phase difference between the two signals output from the differential amplifier is π/2. To obtain direction judgment and counting pulses, these two signals need to be shaped, first into square waves with a duty cycle of 1:1. Then, by comparing the phase of the square waves, the moving direction of the linear encoder can be determined. By counting the square wave pulses, the displacement and speed of the linear encoder can be obtained.

GTM sensor usage precautions

When plugging or unplugging the connector between the linear encoder sensor and the digital display unit, ensure the power is turned off. Install a protective cover whenever possible, and promptly clean chips and oil splashed onto the scale to strictly prevent any foreign matter from entering the housing of the linear encoder sensor. Regularly check whether the mounting screws are loose. To extend the service life of the dust-proof sealing strip, apply a thin, even layer of silicone oil to the strip, taking care not to splash it onto the glass grating ruling surface. To ensure the reliability of the linear encoder sensor, clean and wipe the linear encoder scale surface and the index grating surface at regular intervals with an ethanol mixture (50%) to keep the glass grating scale surface clean. The linear encoder sensor must not be subjected to severe vibration or impact, as this may damage the linear encoder; if the linear encoder breaks, the sensor will fail. Do not disassemble the linear encoder sensor yourself, and never arbitrarily change the relative gap between the main scale and the secondary scale. Otherwise, this may compromise the accuracy of the linear encoder sensor and cause relative friction between the main scale and the secondary scale, damaging the chrome layer and thus the grating lines, resulting in scrapping of the linear encoder. Take care to prevent oil stains and water from contaminating the linear encoder scale surface, as this may disrupt the distribution of the grating lines and cause measurement errors. The linear encoder sensor should avoid operating in environments with severe corrosion to prevent corrosion of the grating chrome layer and the linear encoder surface, which would degrade the quality of the linear encoder.

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