How Gascheck Tesla Works; Thermal Conductivity - ion science GasCheck Tesla Instrument User Manual

How GasCheck Tesla works

Thermal Conductivity

All gases conduct heat but by varying amounts, if an object is heated and then the source of heat is removed, the
object will eventually cool down to match ambient air temperature. This action occurs because the ambient air
surrounding the object carries the access heat into the surrounding atmosphere.
This principal is also the same for objects that are cooler than the surrounding ambient air.
Dissipation of heat into an air atmosphere is known and is a predictable rate however, if the ambient air is replaced
with an alternative gas like Helium the rate at which an object cools down changes.
If the object mentioned above had its environment replaced with pure Helium it would cool down to the environment
temperature about 6 times faster.
The GasCheck Tesla contains a heated thermistor bead that transmits heat to a block of material that remains at a
constant temperature. As air passes through the detector chamber a constant amount of heat passes from the bead
to the block. Gases that are different to air will affect the rate at which heat transmits from the bead to the block,
these rates of change are measured and displayed as leak rates.
The diagram below shows the basic functionality of the GasCheck Tesla 's Thermal Conductivity sensor.
A fan draws a small flow of gas through the probe and into the sensing chamber. The thermistor bead heats up when
electrical power is applied. As air passes through the cell a constant level of heat is transmitted to a Temperature
Stable block through the air, this rate of heat transmission is used to 'Zero' the instrument.
When gases with different thermal qualities pass through the chamber the amount of heat being transmitted to the
Temperature Stable block changes. These changes are measured, calculated and displayed on GasCheck Tesla as leak
rates or gas concentrations.
NOTES:
- Some gases have similar thermal properties to that of air, therefore the GasCheck Tesla can only detect larger
concentrations of these gases.
- Some gases have positive and other gases negative signals. To simplify the instruments function GasCheck Tesla only
displays changes as positive readings.
- The GasCheck Tesla can NOT differentiate between gases! Selecting a specific gas on the GasCheck Tesla allows the
instrument to calculate concentrations of that gas only if that gas is being detected.
Unrivaled Detection.
Air flow
Probe
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GasCheck Tesla Instrument User Manual V1.2R
Temperature
Stable
Display
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