The WRM-HV series of precision metal film MELF resistors has been launched by TT Electronics. With over double the standard voltage rating and a value range from 340k to 3.4M, WRM-HV provides surge tolerant, high stability solutions for high voltage measurement and precision analogue circuits. For use chiefly in the market segments of industrial, instrumentation and medical, the resistors will be of particular interest to designers of energy meters, measurement instruments and process monitors.
Providing a combination of high operating voltage, high precision and tolerance of surge conditions, the WRM-HV resistors are suitable for measuring supply line voltage levels in energy metering and power condition monitoring. They can also enable low noise regulation of high voltage power supplies in laboratory and medical applications.
Factors driving the demand for this kind of device are the growth in smart meters both for billing and for site or process energy management, and the demand for high stability high voltage power supplies.
TT Electronics’ WRM-HV resistors are able to operate at voltages up to 1kV - over double the rated voltage of standard types. This allows fewer parts to be used in series chains for high voltage measurement, saving component count, space, BOM and overall cost.
Rated at 0.4 and 1W at 70°C, the resistors are offered in the popular 340K to 3M4 range and complement the existing WRM series with a high voltage version of the larger two sizes, 0204 and 0207. Value identification is by way of the normal resistor colour coding.
With precision specifications of ±0.1% and ±25ppm/°C, the resistors free up a designer’s error budget enabling savings to be made elsewhere in the circuit. Also, the resistors’ surge tolerance enhances reliability and reduces field failures.
WRM-HV offers a higher rated voltage than most MELF resistors and a higher 1.2/50µs lightning strike surge maximum voltage than key competing parts.
Physically comprising a homogeneous sputtered metal alloy film on a high-grade ceramic rod with value precision adjusted by laser, the terminations are plated steel caps and the pure tin finish produces ageing free contacts on which low melting solders can be used.
TT Electronics’ WRM-HV series provides a combination of precision, high voltage rating and tolerance to surges.