Introduction

The VIM-1 system is a molecular drag manometer also for non-laboratory applications, uses a spinning sphere as a pressure sensor. The two part sensor design is based on the well-established Spinning Rotor Gauge (SRG), offering excellent reproducibility and high reliability, especially for monitoring static vacuum systems in industrial applications.

The VIM-1 sensor head is designed for robust operation even under rough conditions. All parameters are measured by the head´s readout, thus no external signal is needed. The measurement principle is contactless, and without any change of material constants, simply by measuring the rotation frequency change of a ball in vacuum. Therefore, there are no thermal or ionization effects as with many other gauges to influence measurement accuracy or degrade from aging over time.

The VIM-1 sensor offers higher tolerance to vibrations and negligible differences with imperfect vertical alignment. The sensor ball is retained securely in position by a strong magnet as part of the protective cover, so shock and vibration in mobile applications will not affect accuracy and performance.

User-friendly control unit and readout with one-button operation is easy to operate, even by untrained personnel.

One sensor head can be used for multiple Sensor tubes, all measurement relevant parameters are specific to the ball only. Therefore, every Sensor head can run each Sensor tube as well.

VIM -1 System

The VIM-1 vacuum measurement system consists of a measuring head, control unit, and stainless steel measuring tube containing a 4.5mm stainless-steel ball-bearing serving as the pressure sensor.

During measurement, the sensor ball is accelerated by electromagnetic force to a speed of 600 revolutions per second (rps), levitated by a magnetic field, and rotates freely with virtually no friction. The ball is then allowed to coast as it measures viscous (molecular) drag caused by incident gas molecules inside the measuring tube.

Measurement time is about 10 seconds and above (for a variability of +/-3% to +/-10% of reading, between 0.1mbar and 10-6 mbar and without zeroing). More stable and accurate values may be achieved by extending the measurement time and zeroing the system (residual drag).

As long as the sensor ball is properly handled, its friction coefficient does not change over time. The VIM-1 thus exhibits excellent long-term stability and reproducibility. The unit requires no recalibration under normal usage. If required, sensor ball may be replaced at relatively low cost.

One Sensor head can be used for multiple sensor tubes without any loss of performance, as all measurement relevant parameters are properties of the ball. A protection cap and a magnet protect the Sensor and its tube during transportation or after measurement.

The control unit accommodates a 32-bit microcontroller, power supply and measurement electronics, more than 1000 measurements can be saved. RS-485 interface allows linking of control units for simultaneous monitoring of multiple vacuum changes or for remote readout over distances up to one km (0.6 mile). Bright, clear display shows pressure in Pa, hPa / mbar or Torr.

The system can be fully operated and set up remotely by a GUI from a PC.

 

Sensor Setup

The sensor can be delivered with standard KF 25 flanges. However, to minimize permeation through elastomers it is recommended to metal-seal the sensor by welding it onto the vacuum chamber, especially to achieve horizontal configuration. For improved mechanical stability, a protective cap can be screwed on the sensor flange, a concept used on gas bottles.

A second option is to use a glass tube with the ball inside which is welded to the system. It is used for manufacturing and quality control and can be removed before shipment.

In this case the sensor is a disposable by the OEM, based on our application support.

Measurement performance

The SRG Technology can reach Transfer standard accuracy/ reproducibility with a long term stability in years. For many industrial and static vacuum applications the intrinsic accuracy and reproducibility of the sensor is sufficient, without any calibration or zeroing, 6 decades measurement range at approx.

10% of reading accuracy exceed requirements. Once the Sensor is zeroed, and the calibration factor stored, one can achieve accuracy in the 1% of reading range.

FeaturesBenefits
Separation from inexpensiv sensor and more costly electronicsNo need to open the sealed vacuum chamber
Ideal for monitoring sealed vacuum systems
Easy to connect to port
No electrical feedthroughsChamber remains stably sealed even after thermal stress
Electromagnetic/Mechanical measurementDoes not affect pressure or gas composition
Insensitive to vacuum process and temperature conditions
All-metal Sensor (in metal or glass tube)Contactless measurement provides long-term stability
High accuracy and precision direct vacuum measurement
No component to fail or replace
Cost effective Sensor concept
Glass sensor tube maybe removed and be disposed of before shipment
Very clean and sterile concept
Weldable sensor solution
Removeable Sensor head/readoutElectronics remain protected
Measurement and mounting on demand
One head for multiple sensors
Heads are universal, fit all sensors
High intrinsic accuracy/reproducibilityNo adjustments: Sufficient intrinsic accuracy for most applications
Long term stability for years
No electronics remain after measurementCorrosion, radiation (UV, ...) and temperature resistant
One-button operationNo special training or specialist needed
Protection cap and magnet for storageNo breakage risk or damage of the ball´s surface
Remote PC controlUser friendly
Serviceable sensorQuick and easy to clean and reassemble
Single connection to multiple units via RS-485 interfaceSimultaneously monitors multiple vacuum chambers

System Specifications
Measurement range10 to 5 × 10-7 mbar (7.5 to 3.7 × 10-7 Torr)
Specified measurement range0.1 to 1×10-6mbar (0.075 to 0.75×10-6 Torr)
Measurement principletransfer of momentum between contactless spinning ball and gas molecules
Accuracy1 % of reading
Long term stability<1 % drift per year
Sensor
Operating / bakeout10 to 50°C / 450 °C
Wetted Material tube/ballStainless Steel
Protection EN 60529/A2:2013IP68
Mounting positionHorizontal
Readout/Power Supply/Head
Display6-digits LED
InterfacesUSB 2.0, RS485, RS232 printer port
Relays2 SPTD, 48VDC 0.5A
Internal storage with time stamp1023 values
Remote Control / GUIWin 7/8/10
Humidity, IEC 68-2-3898%, non-condensing
Operation10 to 40°C
Supply Voltage/Frequency85 – 256 VAC, 47-63Hz
Certifications
CEEN61000-6-2, EN 61000-6-3

Temperature Directive 97/23/CE
RoHSDirective EU 2015/863

Ordering Information
VIM – 1 SystemOrdering code
System includes Power Supply/Readout, Cable, HeadVIM-Pr-001
Sensor Tube/Ball
Sensor with welding tube, incl. mechanical protectionSEN-SK-001
Sensor with welding tube, w/o mechanical protectionSEN-ST-001
Sensor with KF 25, w/o mechanical protectionSEN-25-001
Warranty extension
Warranty extension 2 years (max 10 years total)GEW-2J-001
Warranty extension 4 years (max 10 years total)GEW-4J-001