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The Rosemount transmitter series comes in a wide variety of types. These include intelligent Rosemount transmitters, Rosemount temperature transmitters, Rosemount pressure transmitters, Rosemount level transmitters, Rosemount differential pressure transmitters, and so on. You may be familiar with many of these transmitters, but there are also some Rosemount products that are less well-known. Below is a brief introduction to the basic information regarding these products: 1. Ultrasonic transmitters among Rosemount transmitters: Ultrasonic transmitters can be used for measuring levels, quantities, flow rates in channels or open channels, as well as for determining distances. It is smaller in size, lighter in weight, and cheaper in price. Ultrasonic transmitters are divided into two categories: ordinary ultrasonic transmitters (without a gauge) and integrated ultrasonic transmitters, with the latter being more commonly used. An integrated ultrasonic transmitter that consists of a header (such as an LCD display) and a probe, and outputs a 4–20mA signal directly; it combines a miniaturized sensitive element (probe) with electronic circuits. 2. Rosemount transmitter’s antimony electrode acidity transmitter: an industrial online analysis instrument that combines pH detection, automatic cleaning, and electrical signal conversion; it is an acidity transmitter for pH measurement systems consisting of an antimony electrode and a reference electrode. The solid-state module circuit in this acidity transmitter is made up of two main parts. For safety during on-site operation, the power supply section uses 24V AC to power the secondary instruments. In addition to providing the driving power for the cleaning motor, this power supply must also be converted into the appropriate DC voltage through a current conversion unit for use by the transmission circuit. In the acidic solution under test, an antimony trioxide oxide layer forms on the surface of the antimony electrode, thereby creating a potential difference between the surface of the metallic antimony and the antimony trioxide. The magnitude of this potential difference depends on the concentration of antimony dioxide trioxide, which corresponds to the concentration of hydrogen ions in the acidic solution being tested. If the activities of antimony, antimony trioxide, and aqueous solution are all set to 1, their electrode potentials can be calculated using the Nernst equation. The second part is the measurement transmitter circuit, which amplifies the reference signal from the sensor and the PH acidity signal, and then sends them to the slope adjustment and positioning adjustment circuits, thereby reducing the internal resistance of the signals and allowing it to be adjusted. The amplified PH signal is combined with the temperature-compensated signal, then fed into a differential conversion circuit; finally, a 4–20mA constant current signal corresponding to the PH value is output to the secondary instrument in order to enable display and control of the PH value. 3. Rosemount transmitters for measuring acid, alkali, and salt concentrations: These transmitters enable continuous online detection of the concentration of acids, alkalis, and salts in aqueous solutions during industrial processes. They determine the concentration by measuring the electrical conductivity of the solution. The working principle of acid, base, and salt concentration transmitters is that, within a certain range, the concentration of acid or base solutions is proportional to their conductivity. Therefore, by measuring the value of the solution’s conductivity, it is possible to determine the level of acidity or alkalinity. When the solution under test flows into a dedicated conductivity cell, if electrode polarization and distributed capacitance are ignored, it can be treated as an equivalent pure resistor. When a constant-voltage alternating current flows through it, the output current is linearly related to the conductivity, which in turn is proportional to the concentration of acids and bases in the solution. Therefore, by measuring the solution current, the concentrations of acids, bases, and salts can be calculated. These transmitters are primarily used in industrial processes such as boiler feedwater treatment, preparation of chemical solutions, and environmental protection. Acid, alkali, and salt concentration transmitters are mainly composed of a conductivity cell, an electronic module, a display gauge, and a housing. The electronic module circuit consists of units such as an excitation power supply, a conductivity cell, a conductance amplifier, a phase-sensitive rectifier, a demodulator, temperature compensation, overload protection, and current conversion. 4. Rosemount conductivity transmitters: These are process instruments (integrated transmitters) that enable continuous online measurement of the conductivity of aqueous solutions in industrial processes. By measuring the conductivity of the solution, it is possible to indirectly determine the ion concentration. To distinguish them from metal conductors, the electrical conductivity of electrolyte solutions is expressed as conductivity (the reciprocal of resistance) or specific conductivity (the reciprocal of resistivity). Since an electrolyte solution is a good conductor of electricity just like a metal conductor, there must be resistance when current flows through it, and Ohm’s law applies. However, the resistance-temperature behavior of liquids is opposite to that of metal conductors, exhibiting a negative temperature coefficient. When two mutually insulated electrodes form a conductivity cell, and a solution to be tested is placed between them with a constant-voltage alternating current applied, an electrical circuit is created. If the voltage magnitude and electrode size are fixed, there is a certain functional relationship between the loop current and conductivity. In this way, by measuring the current flowing through the solution to be tested, its conductivity can be determined. The structure and circuit of the conductivity transmitter are the same as those of the acid, alkali, and salt concentration transmitters. 5. Rosemount transmitters with thermistor isolation: The RTT2 type of thermistor isolation transmitter is primarily used in control systems, and it is widely applied in distributed control systems (DCS), supervision and data acquisition systems (SCADA), environmental monitoring systems (EMCS), etc.; its output is linearly related to temperature. It isolates the input, output, and power supply from one another; it converts a set of thermal resistance signals from the field into two sets of 4-20mA standard current signals, which are then transmitted in an isolated manner to control devices such as DCS systems in the control room. 6. Rosemount capacitive level transmitters: Suitable for industrial enterprises to carry out measurements and control during the production process; they are primarily used for the remote, continuous measurement and indication of liquid levels in conductive and non-conductive media, as well as of levels of granular solids. A capacitive sensor consists of an insulating electrode and a cylindrical metal container filled with a measuring medium. A capacitive level transmitter consists of a capacitive sensor and an electronic module circuit. It operates on a two-wire 4–20mA constant current output as its basic configuration; after conversion, it can also provide outputs via three-wire or four-wire connections, with the output signal taking the form of standard signals such as 1–5V, 0–5V, or 0–10mA. As the material level rises, since the dielectric constant of non-conductive materials is significantly lower than that of air, the capacitance changes as the height of the material changes. The modular circuit of the transmitter consists of units such as a reference source, pulse width modulation, conversion, constant current amplification, feedback, and current limiting. The advantages of using the pulse width modulation principle for measurement include a lower frequency, resistance to RF interference from surrounding components, good stability, good linearity, and no significant temperature drift. The above are brief introductions to several less common Rosemount transmitters. It is hoped that through these introductions, people will gain a deeper understanding not only of the more common transmitters but also of the less common Rosemount transmitters, thereby enhancing their overall knowledge of the transmitter industry.