VSLT Calibrated Helium Leaks


The VSLT Adjustable (Variable) Leak-Rate Calibrators have been developed specifically to calibrate sniffer leak detectors and are designed with Teflon-permeation leak rate control elements to avoid the clogging problems common to Calibrators that have capillary leak elements. This is particularly important for small leak rates and industrial use.

The VSLT Accu-Flow™ Calibrated Leaks are available for adjustable leak rates in limited ranges within the usual values for “Sniffing” of 10-4 to 10-6atm-cc/sec, as shown on the “Ordering” page linked above.

VTI calibrates each leak at three pressures/leak rates and provides a curve of leak rate vs. pressure. Using the curve, the fill/exhaust valve and the integral pressure gauge (to preserve NIST-traceability), the user changes the Helium pressure in the VSLT reservoir to obtain the specific leak-rate desired.

Additional Information

Why choose the VSLT Calibrator?

WILL NOT CLOG OR BREAK – permeation leak element
ADJUSTABLE LEAK RATE – by changing the pressure
LONG TERM STABILITY – Low depletion rate
CAN BE SET TO AN EXACT LEAK RATE – without the usual manufacturing variance
REFILLABLE RESERVOIR – from the user’s gas supply
WIDE LEAK-RATE CHOICE – the full range that is used for sniffing
NO FALSE READINGS – no large dead spaces
EASY PROBE LOCATION – for repeatable results
MEETS ISO REQUIREMENTS – NIST-traceable, A2LA-accredited Calibration Certification

Using the Calibrator

To calibrate a Helium Sniffer Leak Detector, the operator places the tip of the sniffer probe briefly into the tapered recess at the point source of gas flow of the VSLT. The leak-rate reading of the Detector is then adjusted to the Leak Rate of the Calibrator, as provided by VTI on the Calibration Tag. A second reading is obtained in the same way to assure the calibration of the detector.

You should compare the VSLT periodically to another Calibrated Leak if available, and return it to VTI for recalibration in accordance with your Quality Assurance/ISO schedule requirements.

Ordering Information

The VSLT Calibrators can be ordered for various adjustable leak-rate ranges commonly used for sniffer-type leak detection. When ordering or requesting a quotation, please provide the Part Number and also specify the Approximate Leak-Rate Range requested including your preferred leak-rate Units (for example, “approximately 3 to 8 x 10-5 atm-cc/sec”). The Range specification is “approximate” because the minimum and the maximum value of the range will vary slightly for individual leaks due to the Manufacturing Variance. The leak-rate range available for each VSLT Leak is limited to somewhat less than a factor of 10, so the leak-rate range should be specified as approximately 1 to 6, 3 to 8, or 4 to 9 x 10-x atm-cc/sec.

A leak-rate range extending between two decades can also be requested, such as from 6 x 10-6 up to 3 x 10-5 atm-cc/sec. (This is also an appropriate way to order a VSLT if you want to be able to obtain an exact leak rate of 1.0 x 10-5 atm-cc/sec.) An alternative specification is to identify the “Central Leak Rate” for a VSLT Leak, such as 5 x 10-5 atm-cc/sec, and VTI will build the Leak to provide that leak-rate at a mid range pressure on the 400-psig gauge. Using additional calibrations at a lower and higher pressure, the total leak-rate range of the Leak then extends above and below this central value. For each VSLT Leak, it is noted that exact leak rates like 4.5 x 10-5 can be obtained within its available range.

Various leak-rate units can be specified and the calibration data will then be reported in the units requested. Please contact us for assistance if you have any questions or want a customized VSLT Leak.

“Special Orders” are everyday products for us! Just let us know what you need!


Without requiring specification, the VSLT Model Calibrator always has a fill/exhaust valve to allow the users to exhaust gas from its 110 cc reservoir to lower the leak rate, or to refill the reservoir to a higher pressure (using their clean gas supply) to increase the leak rate. The 400-psig pressure gauge on the VSLT is used in VTI’s NIST-traceable Leak-rate Calibrations and preserves the NIST-traceability of the calibration for the user as the pressure and leak rate are varied.

Part Number Build-Up

The VSLT Series Part Numbers are constructed as follows:


where X = the code for the Leak Rate “Decade” within which an adjustable range of leak-rates is being requested

where 3C = three calibration points

where HE = Helium gas leak

The X codes are listed below. As noted above, the actual range of leak rates requested within that decade/range should also be specified.

Leak-Rate Ranges and Part Numbers for VSLT Model Leaks

Examples of Requested Leak-Rate Ranges: Leak-Rate  Code (X): Example Part Number:
1 to 6×10-4 atm-cc/sec 4  VSLT-4-3C-HE 
6×10-4 to 3×10-5 atm-cc/sec 4/5  VSLT-4/5-3C-HE 
3 to 8×10-5 atm-cc/sec 5  VSLT-5-3C-HE 
6×10-5 to 3×10-6 atm-cc/sec 5/6  VSLT-5/6-3C-HE 
3 to 8×10-6 atm-cc/sec 6  VSLT-6-3C-HE 
4 to 9×10-7 atm-cc/sec 7  VSLT-7-3C-HE