The Pressure restrictor has a standard DIN fitting which can be used directly into a DIN pillar valve or into an A clamp (yoke) with a DIN Female fitting.
The pillar valve is opened gently until the gas can just be heard hissing through the tubing. Close after five seconds. Watch reading, it should rise and reach a stable level. If it reaches a maximum and then falls back, the cylinder has been opened too much. After the reading stabilizes (about 10 seconds) open valve again for 5 seconds as above. The reading should this time peak and fall back less than .5%. The stable reading is the oxygen level in the gas. If in doubt this step can be repeated as many times as necessary. The stable reading is correct. The secret to accurate fast measurements is gently opening the pillar valve enough to obtain a gas flow of about 2 liters per minute (a low level hiss).
The pressure restrictor is used to achieve low flow rates of gas from the cylinder. The Flow Thru divertor is a set of blades which divert the gas down onto the sensor face. The gas is turbulent and ensures a fast reading. The tubing is added to prevent air being drawn into the Tee outlet and reducing the reading. Any poor joints will create a venturi action and suck in air.
NB: The system should be calibrated in air 20.9% before use. The measured gas should be within 1% of the calculated mixture. If a discrepancy of more than 1% if found check the analyser in 100% O
2 and Air (20.9% O2). DO NOT ASSUME THE ANALYSER IS CORRECT
External Sensor:
Sensors have two membranes and the sensor requires ambient pressures on the rear to equalize pressures. Sensors respond to Partial Pressure changes so any build up of pressure inside the sensor will appear as an increased electrical output.
The user easily changes the remote sensor. To many people the sensor is the least understood and therefore it is the first thing to be suspected when things go wrong. VN2O2 sensors can be quickly exchanged without opening the instrument case. No tools are required. The user can change sensors in seconds.
The Vandagraph Ltd. Analyzer is always vulnerable during measurement. Single handed calibration can be difficult in certain diving activities. The lightweight sensor can be left on the cylinder and the analyzer can be laid on a nearby surface allowing both hands to be free.
Moving gas always generates pressure that is interpreted by the instrument as an Oxygen percentage so ideally the calibration and measurement should always be made in a still gas.
This is the reason for advising the use of either the DIN Kit or a plastic bag with small holes. Any system with a restrictor and continuous flow requires a constant pressure to produce constant flow. This flow rate must also be used during calibration in air for true accuracy. Most of the currently available flow restrictors depend on their ability to reduce the flow to between 0.5 and 2.0 Litre per minute either straight from the cylinder or from the direct feed.
With either method, time is required to achieve an accurate measurement.
- Flush system out with air for the recommended time (a minimum of 30 seconds)
- Connect the cylinder to be measured
- Flush out with gas for recommended time
- Calibrate in Air to check calibration has not changed
Auto switch-off on the VN202:
Attention during measurement is rightly concentrated upon accuracy and correct use. Auto switch-off removes one more problem for the diver. A by-product is increased battery life.
Instruction Booklet supplied with the VN202:
This informative booklet is specifically written for divers and gas mixers.
Carrying/Storage Case:
This is the safest place to carry and store the Oxygen Analyzer and its accessories.
Lifetime Warranty Program available on request
Specifications |
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| Range: 0-100% oxygen |
Battery Life: 12 months (typical) |
CONTACT: IANTD 9628 NE 2nd Ave. Suite D Miami Shores, FL 33138 USA Phone: (305)751-4873 Fax: (305)751-3958 |
| Accuracy: +/- 1% of full scale |
Auto Swith Off: 2-3 minutes |
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| Response Time: 90% in less than 10 seconds |
Sensor Type: R-17 (Galvanic) |
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| Resolution: .1% |
Sensor Life: Expected 48 months in air 10 months in 100% oxygen |
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| Operating Temperature
Range: 0-40 oC. |
Dimensions: 60mm X 120mm X 25mm |
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| Battery Type: 9 volt alkaline |
Weight: 205gm ind. battery & sensor |
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| Cable Length: 250mm - 759mm |
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Parts List |
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| VN202 Analyser | * A-268 Tee Adaptor | * DM22M10 Male Adaptor |
| R-17 Micro Fuel Cell | * B-50057 Flow Thru Divertor | * BS111 Viton™** O Ring |
| DINKIT Restrictor Kit | * VP 12 Tubing 30 cm | * DIN22F High Pressure Restrictor |
| VNR1 Large Case | * ITEMS ARE INCLUDED
IN THE DINKIT **Viton™ is a registered trademark of DuPont Dow Elastomers. |
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