Emerson NGA2000 PMD Benutzerhandbuch

748461-B 

April 2003 

 

http://www.processanalytic.com 

Model NGA2000 PMD, NDIR 

 

 

This addendum serves as an amendment to 
the Model NGA 2000 PMD and NDIR instruc-
tion manuals.  The following information 
should be considered part of the manual, if 
your instrument has a Vaisala Barometric 
Pressure Transducer installed in it, or if you 
are retrofitting a PMD or NDIR with a Vaisala 
transducer kit. 

The Vaisala PTB100 series Analog Barometer 
is a N.I.S.T. traceable precision silicon capaci-
tive atmospheric pressure transducer. The 
sensor delivers an analog voltage output that 
is inversely proportional to its inlet pressure. It 
has an operational ambient pressure range of 
800 to 1060 hPa. 

The original PMD and NDIR instruments were 
designed for use with a resistance bridge type 
of pressure transducer requiring an external 
gain amplifier with an offset trim The Vaisala 
transducer contains an integral gain amplifier 
that is scaled for a 0 to +5 Vdc output.  The 
661380  “Interface Board” contains the cir-
cuitry to convert the Vaisala single ended 0 to 
+5 V dc output into the referenced bridge 0 to 
+0.625 V dc output configuration that is re-
quired by the Analyzer module’s Computer 
Analysis Board.  The Vaisala transducer kit is 
backward compatible with the original Rose-
mount pressure transducer. 

The Vaisala Interface Circuit board adapts the 
single ended analog output of the Vaisala 
sensor into a Precision Voltage referenced, 
balanced bridge (at 1 atmosphere) input con-
figuration. A “Bridge Balance” pot on the 
Vaisala Interface Circuit board provides the 
fine trim “Bridge Balancing” calibration ad-
justment that is required to set up each indi-

vidual transducer at a known ambient air 
pressure. Test points are provided on the cir-
cuit board for this adjustment.   

The Vaisala transducer output range is 0 to 
+5 Vdc. 

The Vaisala analog output voltage is inverted 
and fed into a balanced summing node that is 
referenced by a precision regulator. The 
summing node voltage is 0.000 Vdc at 1013 
hPa (1 atmosphere ambient air pressure). The 
summing node voltage is then buffered, in-
verted, and gain reduced by a factor of 8 to 
produce the Pressure Compensation Output 
voltage at J12-1 for the Computer Analysis 
board.  

Low noise, Low input current offset Op-Amps, 
and common substrate resistors are used to 
reduce gain tracking errors and null thermal 
coefficient effects. 

1.  Remove the original Rosemount trans-

ducer circuit board assembly, located on 
the motherboard at J12 and J13 (if pre-
sent). 

2.  Install the transducer with the pressure 

inlet facing the rear of the instrument us-
ing the mounting studs provided on left-
hand side of the detector housing. 

3.  Install the Interface board into it’s mating 

sockets (J12 and J13) on the mother-
board. 

4.  Connect the 4-pin cable (P1) from the in-

terface board (noting pin polarity) to the 
Vaisala Pressure Transducer.