21 PRO

Pressure transmitter 1 to 400 bar 20 to 120% 4 to 20 mA loop power

Piezoresistive pressure transmitters
Standard and programmable (pro) versions

The KELLER Series 21/21PRO are extremely reliable and cost effective pressure transmitters. These pressure transmitters use a programmable KELLER-ASIC microchip called ”ProgRes” (programmable resistors). The ”ProgRes” chip enables the transmitters to be set up and calibrated using automated test equipment, for improved product quality and lower costs. The PRO versions also have the unique feature that they can be programmed or reranged by the end user, via the hand held PP-96 programmer. Since its first introduction in 1989, the Series 21/21PRO was an immediate success, thousands of transmitters and hundreds of programmers are in daily service worldwide.
This transmitter uses the KELLER Series 6SC capsule as the core. The sensor is a piezoresistive silicon pressure sensor, mounted in an oil filled capsule. The media pressure is isolated by a stainless steel diaphragm and transferred to the silicon sensor hydraulically via the oil. Sealed Gauge versions have a TAB (Tape Automated Bonding) sensor floating freely on a flexible print in the oil, this guarantees stability and endurance. Test have shown that even 20 million cycles of rapid changes in pressure from 10 bar to 250 bar do not cause damage to these sensors, and the Series 21 is therefore ideally suited for the toughest hydraulic applications.
The ”ProgRes” circuit has programmable resistor networks, to set the Zero / Gain and thermal coefficients. All Series 21/21PRO transmitters are subjected to comprehensive test procedures which cycle both pressure and temperature, the various parameters are then automatically calibrated and set by the computer controlled test rig at the end of the run. A final test then checks that the settings are correct and within specification, only then are the transmitters are released for use. Note: The standard Series 21 transmitters are NOT user programmable. The programmable version transmitters, Series 21PRO has the data lines brought out to an Amphenol 8pin connector, allowing simple and precise adjustment of Zero and Span. The KELLER Programmer PP-96 is used to facilitate programming of individual transmitters. The PP-96-10 can handle up to 10 identical transmitter at one time. The signal output of a PRO version transmitter may be adjusted to give full-scale between 25% and 120% of the nominal range, and ±25% zero adjustment.

Datasheet: kel21.pdf