NH00 switch, German SIBA, model NH00, price

The NH00 switch is used to detect angles. It has a hole in its body that fits LEGO axles. When connected to RCX, the angle switch counts once for every 1/16 rotation of the axle. Rotating in one direction increases the count; reversing the direction decreases it. The count depends on the initial position of the angle switch. Upon initialization, the count is set to 0. If needed, you can reset it via programming.

NH00 switch classification

1) Contact type: The sensing element of a contact temperature switch makes good contact with the object being measured; it is also called a thermometer. Thermometers reach thermal equilibrium through conduction or convection, allowing the reading to directly indicate the temperature of the measured object. They generally offer high measurement accuracy. Within a certain temperature range, thermometers can also measure internal temperature distribution. However, significant measurement errors occur with moving objects, small targets, or objects with very low heat capacity. Common thermometers include bimetallic, glass-liquid, pressure-type, resistance, thermistor, and thermocouple types. They are widely used in industrial, agricultural, and commercial sectors, as well as in daily life. With the extensive application of cryogenic technology in national defense, aerospace, metallurgy, electronics, food, pharmaceuticals, petrochemicals, and superconductivity research, low-temperature thermometers capable of measuring temperatures below 120K have been developed. Examples include low-temperature gas, vapor-pressure, acoustic, paramagnetic salt, quantum, low-temperature resistance, and low-temperature thermocouple thermometers. Low-temperature thermometers require small sensing elements with high accuracy, reproducibility, and stability. Carburized glass resistors, made by carburizing and sintering porous high-silica oxygen glass, are one type of sensing element for low-temperature thermometers, suitable for measuring temperatures in the range of 1.6 to 300K. 2) Non-contact type: The sensing element does not touch the object being measured; these are also called non-contact temperature measuring instruments. They can measure the surface temperature of moving objects, small targets, objects with low heat capacity or rapid temperature changes (transients), and temperature field distributions. The most common non-contact instruments are based on blackbody radiation laws and are called radiation thermometers. Radiation thermometry includes brightness methods (see optical pyrometers), radiation methods (see radiation pyrometers), and colorimetric methods (see colorimetric thermometers). Each method measures only luminance, radiation, or colorimetric temperature. True temperature is obtained only when measuring a blackbody (an object that absorbs all radiation and reflects no light). To determine the true temperature of an object, correction for material surface emissivity is required. Surface emissivity depends not only on temperature and wavelength but also on surface condition, coatings, and microstructure, making precise measurement difficult. In automated production, radiation thermometry is often used to measure or control surface temperatures, such as steel strip rolling temperature, roll temperature, forging temperature, and molten metal temperature in furnaces or crucibles in metallurgy. In these cases, measuring surface emissivity is quite difficult. For automatic measurement and control of solid surface temperatures, additional mirrors can be used to form a blackbody cavity with the measured surface. Additional radiation increases the effective radiation and effective emissivity of the surface. Correcting the measured temperature using the effective emissivity yields the true surface temperature. A typical additional mirror is a hemispherical mirror. Diffuse radiation from the surface near the sphere's center is reflected back by the hemisphere, increasing the effective emissivity, where ε is the material surface emissivity and ρ is the mirror reflectivity. For radiation measurement of the true temperature of gases and liquids, a heat-resistant tube can be inserted to a certain depth to form a blackbody cavity. The effective emissivity of the cylindrical cavity at thermal equilibrium with the medium is calculated. This value is then used to correct the measured cavity bottom temperature (i.e., medium temperature) to obtain the true medium temperature.

NH00 switch usage precautions

1) Errors introduced by improper installation: For example, the thermocouple installation position and insertion depth may not reflect the true furnace temperature. In other words, the thermocouple should not be installed too close to doors or heating elements. The insertion depth should be at least 8 to 10 times the diameter of the protection tube. Gaps between the thermocouple protection tube and the wall not filled with insulating material can cause heat loss or cold air ingress. Therefore, gaps between the protection tube and the furnace wall hole should be sealed with refractory clay or asbestos rope to prevent convection of hot and cold air, which affects measurement accuracy. If the thermocouple cold junction is too close to the furnace body, the temperature may exceed 100℃. Thermocouple installation should avoid strong magnetic and electric fields; do not install thermocouples and power cables in the same conduit to prevent interference-induced errors. Thermocouples should not be installed in areas with minimal media flow. When measuring gas temperature in a pipe, the thermocouple must be installed against the flow direction and ensure full contact with the gas. 2) Errors introduced by degraded insulation: If thermocouple insulation deteriorates, excessive dirt or salt slag on the protection tube and terminal board can cause poor insulation between the thermocouple poles and the furnace wall. This is more severe at high temperatures, causing thermoelectric potential loss and introducing interference, potentially leading to errors of hundreds of degrees. 3) Errors introduced by thermal inertia: Thermal inertia causes the instrument reading to lag behind temperature changes, which is particularly prominent during rapid measurements. Therefore, use thermocouples with thinner electrodes and smaller protection tube diameters. If the environment permits, the protection tube can even be removed. Due to measurement lag, the amplitude of temperature fluctuations detected by the thermocouple is smaller than that of the furnace temperature. Greater lag results in smaller fluctuation amplitudes and larger deviations from the actual furnace temperature. When using thermocouples with large time constants for measurement or control, the displayed temperature may show minimal fluctuation while the actual furnace temperature fluctuates significantly. For accurate measurement, choose thermocouples with small time constants. The time constant is inversely proportional to the heat transfer coefficient and directly proportional to the hot junction diameter, material density, and specific heat. To reduce the time constant, besides increasing the heat transfer coefficient, the most effective method is to minimize the hot junction size. In use, materials with good thermal conductivity, thin-walled tubes, and small inner diameters are typically used for protection sleeves. In high-precision temperature measurements, bare-wire thermocouples without protection sleeves are used, but they are prone to damage and require timely calibration and replacement. 4) Thermal resistance error: At high temperatures, ash or dust on the protection tube increases thermal resistance, hindering heat conduction, causing the indicated temperature to be lower than the true value. Therefore, keep the exterior of the thermocouple protection tube clean to minimize errors.

NH00 switch industry applications

Temperature switches were the earliest developed and most widely used type of switch. Their market share far exceeds that of other switches. People began using temperature for measurement in the early 17 century. Supported by semiconductor technology, semiconductor thermocouple switches, PN junction temperature switches, and integrated temperature switches were subsequently developed in this century. When two conductors of different materials are joined at a point and heated, a potential difference appears at the unheated ends. The magnitude of this potential difference relates to the temperature at the measurement point of the unheated ends and the materials of the two conductors. This phenomenon occurs over a wide temperature range. By precisely measuring this potential difference and the ambient temperature at the unheated ends, the temperature at the heated point can be accurately determined. Because it requires two conductors of different materials, it is called a 'thermocouple.' Thermocouples made of different materials are suitable for different temperature ranges and have varying sensitivities. Thermocouple switches have their own advantages and disadvantages; they have relatively low sensitivity, are susceptible to environmental interference signals and preamplifier temperature drift, and are therefore unsuitable for measuring minute temperature changes. The sensitivity of thermocouple temperature switches is independent of material thickness.

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