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Keller Series 26Y

sku Product SKU:  KEL-26Ys

The pressure transmitters Series 26 Y are used in water level measurements that are price-sen
sitive but still require considerable accuracy.
Y-series transmitters have an extremely small temperature error. This is achieved by means of
digital compensation of an all-analogue signal path. The gain and the zero point of the gain circuit
can be influenced by digital/analogue converters. These receive their numerical values from an
EEPROM that is addressed depending on the temperature. A mathematical model for TC zero
and TC gain with any order can therefore be determined in the calibration process and stored in
the transmitter with a resolution of 1,5 K. The accuracy of the end product therefore essentially
depends on the amount of testing and the linearity of the measuring cell.
With the Series 26 Y, the monocrystalline silicon measuring cell is reliably protected from the
measuring medium by a stainless steel diaphragm. The steel diaphragm itself is protected from
mechanical influence by a plastic cap, and has outstanding performance features with regard to
accuracy and stability due to its large diameter of 17 mm

The Y-line transmitters have an extremely small temperature error. This is achieved using an additional circuit containing a temperature sensor that subdivides the temperature range into fields that are 1,5 Kelvin (K) wide. The TK zero and TK compensation values are calculated for each field and programmed into the additional circuit. During operation, these values are fed into the analogue signal path depending on the temperature. Each temperature is the „calibration temperature” for this transmitter. The accuracy thereof is mainly determined by linearity. 120 fields are available, representing a possible temperature range of 180 K. The wider the temperature range, the greater the amount of testing that is needed to minimise the inaccuracy of the mathematical model.

ZAR 0,0000


Keller Series PRD-33X

sku Product SKU:  KEL-PRD-33Xs

The Series PRD-33 X was developed for applications that require a high accuracy differential pressure measurement together with high overload resistance in differential pressure ranges as low as 350 mbar.

The Series PRD-33 X is the result of ongoing development of the KELLER PD-33 X differential pressure transmitter. Thanks to a second integrated pressure sensor, the line, or common mode, pressure can now be measured along with the differential pressure, resulting in several notable features not found in traditional differential pressure transmitters.

For example, compensation for line pressure effect is now accomplished during factory calibration. Moreover, both differential and line (absolute) pressure may be read by the user. In addition, the PRD-33 X features high differential overload resistance; e.g., ± 35 bar with a differential measuring range of only 350 mbar (100:1).

The internal differential pressure sensor element is isolated from the High (+) side media by a compliant stainless steel diaphragm, while the Low (-) side media impinges directly on the back side of the silicon measuring cell. Also isolated from the High (+) side media is the line (absolute) pressure sensor. The floating sensor assembly guarantees maximum decoupling from external mechanical forces.

Another notable feature of the Series PRD-33 X is the robust digital RS485 bi-directional communication interface. Information such as serial number, pressure range, filter settings and process values for both differential and line (absolute) pressures and their temperatures are easily obtained.

This combination of features enables certain measurements not possible with traditional differential pressure transmitters. For example, filling levels in liquefied gas storage tanks, including oxygen, nitrogen, carbon dioxide and argon can now be measured safely, accurately and at reasonable cost.

ZAR 0,0000


Keller Series 33X

sku Product SKU:  KEL-33Xs

Digital Output of Transmitter:

This high precision of 0,01 %FS is available as an option (the standard Series 33 X has an accuracy of 0,05 %FS). These Series are based on the stable, floating piezoresisitive transducer and the newly developed XEMICS micro-processor with integrated 16 bit A/D converter. Temperature dependencies and non-linearities of the sensor are mathematically compensated.

Transmitter with Analog Output:

Integrated in the XEMICS processor is a D/A converter of 16 bit for analog signal outputs of 4…20 mA or 0…10 V. The output rate is 400 Hz. The accuracy is diminished by this converting process by 0,05 %FS. The digital output is available on all transmitters with analog output.


With the KELLER software READ30 and PROG 30, a RS485 converter (i.e. K102 or K107 from KELLER) and a PC, the pressure can be displayed, the units changed, a new gain or zero set. The analog output can be set to any range within the compensated range.

Accuracy and Precision

“Accuracy” is an absolute term, “Precision” a relative term. Dead weight testers are primary standards for pressure, where the pressure is defined by the primary values of mass, length and time. Highest class primary standards in national laboratories indicate the uncertainty of their pressure references with 70 to 90 ppM or close to 0,01%. Commercial dead weight testers as used in our facilities to calibrate the transmitters indicate an uncertainty or accuracy of 0,025%. Below these levels, KELLER use the expression “Precision” as the ability of a pressure transmitter to be at each pressure point within 0.01 %FS relative to these commercial standards. The transmitter’s full-scale output can be set up to match any standard of your choice by correcting the gain with the PROG30 software.

ZAR 0,0000

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