Keller Series 4 LD digital combination transmitter

Keller has launched a fully functional digital combination transmitter for pressure and temperature. In the LD series, all the electronic components are accommodated in a laser-welded stainless steel housing filled with silicone oil.

Measuring 11 mm in diameter, the housing contains the sensor technology, the (mathematical) compensation coefficients, the digital signal processing and the I²C interface for simple, loss-free integration into higher level systems. Made of stainless steel or Hastelloy, the housing not only acts as a Faraday cage but also offers appropriate protection against electromagnetic radiation and potential environmental influences. With Keller’s Chip-in-Oil technology, short signal paths with high impact and vibration resistance are realised.

Six standard measurement ranges extend from 1 to 200 bar with a compensated temperature range of -10 to +80°C. Accuracy is rated as better than ±0.15%FS and a total error band of less than ±0.5%FS is attained between 0 and 50°C. The temperature measurement accuracy is ±2 K.

Transmitters in the series are optimised for battery-powered applications, eg, during A-to-D conversion, current consumption is ~1.5 mA, dropping to ~0.1 μA in ‘idle’ mode. The supply voltage range of 1.8 to 3.6 VDC corresponds to a normal microprocessor environment.

The Series 4 LD is the smallest of four versions. Larger models measuring 15, 17 and 19 mm in diameter are also available for relative pressure measurements, offering an additional temperature range (-40 to +110 °C) without changes to the electrical characteristics.