Transmitter protectors are used to guard against transient overvoltages on communication lines operating in hostile electromagnetic environments. Many transmitters communicate by varying the current in a loop (e.g. four to twenty milliamperes) in response to variations in the parameter begin sensed, i.e., temperature or pressure. Some units have a third line to communicate using a linear, low voltage signal. The 444/1151T and 3044/3051T series overvoltages protectors provide three circuits for protection of a 4-20mA loop and a linear voltage output in Rosemount pressure and temperature transmitters. The classical three element, high energy, primary protector circuits are packaged in a compact, circuit board assembly that mounts diectly inside the transmitter housing. A built-in, bypassed current limiting resistor in the PS+ protection circuit allows convenient insertion of more loop resistance by cutting out the bypass jumper. This is useful in situations where excessive power supply current capacity causes the GDT to continue conducting after a transient event.
The 444/1151T Series are designed to permit use in high and low power versions of both 444 Series Temperature Tansmitters (RL, RD, T, MV, RI, CU, NI, LL, andLM) and the 1151 Series Pressure Tansmitters (DP, HP, Ap and GP). In the 444 or the 1151, it protects the two lines of the 4-20 mA loop. In the low power 444 or 1151, it protects the two power supply lines and the linear output voltage line.
The 3044/3051T Series is designed to permit use in the 3044 CA Temperature Transmitter and the high and low power versions of the 3051 Series Pressure Tansmitters (D, A, and G). Mounted in place of the terminal block assembly, in a 3044CA or 3051C, the 3044/3051T Series protects both lines of the 4-20 mA loop. In a low power 3051C, and intergral third circuit protects the linear output voltage line.
The versatility of these units allows the user to stock one type of protector for multiple, came of lower voltage applications. Protectors come with mounting hardware and detailed installation instructions for each transmitter type it can be used with.

How To Choose a Protector

Select a protector series based upon your transmitter type. Select a protector with a voltage rating equal to or greater than the maximum operating voltage in the application. Typically, this is the maximum voltage of the regulated power supply used to generate the 4-20 mA loop current. for equipment powered from an unregulated power supply or a solar panel, care must be taken to assure the protector voltage rating is greater than the maximum operating voltage under worst case conditions. High line conditions for an unregulated power supply can exceed 120% of nominal in the worst case. Solar panels voltages under full insolation can approach 150% of nominal output voltage.

Installation instructions in Spanish are available upon request.