Combined Pirani/piezoresistive Sensors in a Single Tube
Wide Dynamic Range: 1000 Torr to 10-4 Torr
Automatic Crossover Calibration
Attitude Insensitive
Fast Dynamic Response Time
Bakeable to 250°C
Highly Accurate
Compact Rugged Design
Withstand 150 psi Positive Pressure
Linear Output Signal
The
Model 2002
The Model 2002, Dual Sensor Vacuum Gauge, is a wide range vacuum instrument
consisting of a digital microprocessor-based display unit, two sensing
elements
(micro Pirani and piezo resistive bridge) in a single tube shell, and an
interconnecting cable. Together, these components provide accurate vacuum
measurement over
7 decades of pressure from 10-4 Torr to 1000 Torr. This instrument
is a new design approach based on over 50 years of experience by Hastings
Instruments with well-known pressure measurement techniques. A single tube
contains both a Hastings patented thin film Pirani sensor and a piezo
resistive
sensor in a small, rugged and inexpensive package. The piezo resistive
bridge is a direct force sensor which gives very accurate readings at high
pressures
from atmosphere down to less than 1 Torr without the concerns of gas composition.
The thin film Pirani measures pressures from a few Torr down to less than
l x10-4 Torr. An algorithm residing in the microprocessor ensures
a seamless transition between sensors. Additionally, the two sensor outputs
are used in a cross calibration mode to give even higher accuracy.
New
Sensor Design
The Model 2002 sensors are mounted in a rugged corrosive resistant 316 stainless
steel tube. The small packaging reduces the sensor's internal volume, significantly
improving response time. The tube can be mounted in any orientation with
no effect on calibration and is far more rugged than standard fragile convection
driven Pirani tubes. The two sensors reside on a single Au plated Kovar
header. This header is welded into the stainless tube shell and will withstand
positive pressures of over 150 psi.
Each Model 2002 transducer contains a programmable memory chip (EEPROM).
Stored on the EEPROM are the calibration parameters for both the thin
film
Pirani and the piezo resistive bridge. Also contained on the EEPROM is
identification information which is suitable for use in quality/calibration
programs.
Quick disassembly of the Model 2002 transducer allows the user to bake the
sensors to 250°C. After a bakeout the tube is reassembled and normal
operation is resumed. Several connector configurations are available (1/8"
NPT, 2.75 CF® ,1.33 CF® , KF-16, KF-25, VCR®
or ½" OD tube).
The Model 2002 is ideal for applications that require accuracy without the
expense of costly capacitance manometers and/or small size and rugged construction
without the fragility of bulky convection driven Pirani tubes.
New
Readout Design
Like the transducer, the microprocessor based readout/power supply is constructed
for long trouble free life. Using the supplied gaskets, the controller can
be easily converted into a NEMA 12 rated sealed enclosure. The display consists
of an easily readable large green LED flat panel display with smooth operating
tactile membrane switches for mode, gas, calibration, and set point configuration.
The controller features a 3-digit floating point display, user selectable
units (Torr, mbar, Pa), as well as a convenient user interface for flexible
operation. The controller allows the user to incorporate data acquisition
systems by providing a linear per decade analogue output signal in addition
to three separate TTL input/output signals for maintaining control over
various processes.
Optional
Accessories
The Model 2002 has been designed as a flexible system for easy user configuration.
RS-232/RS-485: The standard base unit can be equipped with a single card
that supports both RS-232 and RS-485 communications standards allowing users
a computer interface to query the Model 2002 and monitor system parameters
such as gas, pressure, set points settings and alarm status directly or
via a network. The RS-485 supports multiple units on a network through Model
2002 and sensor addressing.
Switching Relay: A relay interface board allows the TTL outputs to directly
control two relays. Each set point can be programmed anywhere in the seven
decades of the sensor's operation. Each relay consists off a 2 Form C (DPDT)
relay with the relays wired in parallel. The relays are rated for a maximum
switching current of 250 volts AC (resistive load). For accessory specifications
see Model 2002 instruction manual.
Specifications
Measuring Range
10-4
Torr to 10-3 Torr
Ambient Temperature
Operating Range and Compensation
0°C to 50°C
Accuracy
±1.5% of reading
(1000 Torr to 30 Torr)
±15% of reading (30 Torr to 5 x 10-4 Torr)
(based on Nitrogen @ 23°C)
Output
0.5 - 4.5 volts
(0.5 VDC linear per decade)
Process Control
2 TTL Outputs
1 TTL Auto zero input
Digital Readout
Three green LED(0.6")
- Resolution is a three digit floating point mantissa (plus exponent)
Power
90 - 260 VAC, 50
to 60 Hz, IEC receptacle.
A 6 ft., 3 wire grounded power cord is provided with each unit.
Sensor Mounting
Any position without
recalibration
Sensor Internal
Volume
<1.5 cc
Wetted Material
Silicon Nitride,
Silicon, Gold, Pyrex and 316 stainless steel
Stability with
Voltage Variation
Undetectable change
in reading as power fluctuates
Weight
(Display, cable and sensor)
Net: 2.4 lbs
Shipping: 3.8 lbs
Response Times
(Sensor/Controller)
Step change from
10-3 Torr to 1000 Torr (<=50 msec/<= 400 msec)
Model 2002 Dimensions
(reference only)
Standard DIN 43700
insert (¼" DIN)
Case constructed of NORYL - rated UL-94 V1 (self extinguishing plastic)
Panel Thickness
Adjustable to 3/16
inches. Unit mounts into 3.63 in. (92mm) square hole.
Calibrated for
Nitrogen
Factory calibrated
for nitrogen. Conversion factors for many other gases are selectable
( consult instruction manual).
