MKS MicroPirani 925 Series How to use

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P/N: 100017430
Short form manual
REV: A, December 2009
Product: 925-x1590
I/O connector: 6 pin Hirschmann
Output: 5 (PKR251)
RoHS Compliant
Measuring range (N2and Air): 1×10-5 Torr to Atmosphere
Accuracy(1) (N2) 5×10-4 to 1x10-3 Torr: ±10% of reading
1×10-3 to 100 Torr: ± 5% of reading
100 to Atm.: ± 25% of reading
Repeatability(1) (N2): 1×10-3 to 100 Torr ± 2% of reading
Supply Voltage: 9 –30 VDC
Power consumption: < 1.2 Watt
Fuse (thermal recoverable): 200 mA
Analog output 1: (100 Ω impedance): 3.875 –8.675 VDC
Analog output 1 resolution: 16 bit
Materials exposed to vacuum: 304 Stainless steel, Silicon
SiO2, Si3N4, gold, Viton® (2)
Low out gassing Epoxy resin
Internal volume: KF16 flange 2.80 cm3
KF16 long flange 6.63 cm3
KF25 flange 3.55 cm3
VCR4 flange 1.84 cm3
VCR8 flange 3.06 cm3
Housing material: Stainless steel 304
Weight (925 with KF16): 170g
Operating temperature: 0 to 40 oC
Bakeout temperature (Power off): 85 oC
(1) Accuracy and repeatability values are typical values measure in Nitrogen atmosphere at
ambient temperature after zero adjustment.
(2) Transducer without Viton seal is available for use in UHV applications.
MKS Instruments HPS Products
www.mksinst.com

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The 925 transducer package contains these items:
1 pcs. 925 Transducer,
1 pcs. Short form manual (P/N: 100017430)
1 pcs. Documentation & Software CD (P/N: 100017096)
If any items are missing contact MKS customer service.
This short form manual provides the basic information for simple use and
setup. For system integration and advanced setup refer to Operation and
Installation manual.
The 925 MicroPirani vacuum transducer offers a wide measuring range from
1×10-5 Torr to atmosphere and is based on the measurement of thermal
conductivity in small cavity on MEMS silicon chip sensor.
RS232 or RS485 digital interface
Analog voltage output compatible with PKR251
Standalone use or with PDR900 controller
The user switch can used to perform measurement adjustments. Refer to
Operation and Installation manual before pressing the user switch.
The transducer is factory calibrated when delivered. Additional adjustment is
normally not required. Refer to Operation and Installation manual for
calibration and adjustment recommendations.
Install the 925 away from pumps and gas sources and where vibration is
minimized to give the most representative pressure measurement.
The 925 can be mounted in any orientation, without compromising accuracy
and performance.
The 925 is not intended for use in corrosive or explosive
environments. Refer to materials exposed to vacuum for
process compatibility.
Refer to Operation and Installation manual for installation specifications and
recommendations.

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Use a cable with a female 6-pin connector with strain reliefs to ensure proper
electrical connection and to reduce stress.

Ensure a low impedance electrical connection between the
901P transducer body and the grounded vacuum system to
shield the sensor from external electromagnetic sources.
To comply with EN61326-1 immunity requirements, use a braided, shielded
cable. Connect the braid to the metal hoods at both ends of the cable with
the end for power supply connected to earth ground.
925 I/O Connector (6 pin)
6 pin Hirschmann
PIN
Description
1
Identification resistor 11.1KΩ
2
Analog Output +
3
Analog Output –
4
Power + (9-30 VDC)
5
Power return -
6
Chassis

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The analog pressure output (16 bit resolution) is based on the digital
pressure reading (PR1). Connect the signal to a differential input.

Do not connect the negative side of the analog output to
the power supply return or to any other ground. The
voltage drop from supply current will produce errors in the
analog output.
Converting voltage to pressure:
The 925 provides pressure signal down to 1E-5 Torr.
Pressure (Torr) = 10 (1.667×Vout –11.46)
Pressure (mbar) = 10 (2×Vout –11.33)
Pressure (Pascal) = 10 (2×Vout –9.333)
Vout vs. Pressure (Torr)
Gas dependence
The MicroPirani™transducer is based on measurement of thermal
conductivity and consequently its reading depends on gas type and gas
concentration. The transducer is calibrated for Nitrogen, and will read higher
pressure values when exposed to atmospheric air.
US & ASIA:
MKS Instruments, Inc., HPS™
Products, Inc.,
5330 Sterling Drive, Boulder, CO
80301, USA,
Phone: [phone]
EUROPE:
MKS Denmark ApS
Ndr. Strandvej 119G
DK3150 Hellebaek, Denmark
Phone: [phone],
Email: [e-mail]