4
III
、
Test principle
Using the different leakage currents of the ion current under different vacuum conditions
to test and identify the advantages and disadvantages of the vacuum isolation chamber.
The two contacts of the arc extinguishing chamber are separated by a certain distance,
and the moving contact applies a high voltage pulse to the static contact to apply a
negative ion current. Because the leakage current is very weak, it is susceptible to
different interference from the outside world to reduce accuracy. Therefore, the
excitation coil must be wound outside the arc extinguishing chamber, and a large current
is passed to the coil to generate a pulsed magnetic field synchronized with the high
voltage in the arc extinguishing chamber to accelerate the ion current and enlarge the
sampling rate proportionally. In this way, under the action of the pulsed magnetic field,
the electrons in the arc extinguishing chamber move in a spiral motion and collide with
residual gas molecules to ionize. The ion current generated is approximately
proportional to the residual gas density, that is, the degree of vacuum. For vacuum tubes
with different diameters, under the same vacuum conditions, the magnitude of the ion
current is also different. Through experiments, the corresponding relationship curves of
vacuum degree and ion current of various tube types can be calibrated. When the ion
current is measured, the corresponding internal proportional parameters are called and
accurately calculated to obtain an accurate and true vacuum value. That is to say, the
vacuum degree of the tube is obtained by querying the ion current-vacuum curve of the
tube, and this process is automatically completed by the computer.
IV
、
The main technical parameters
1. Measured vacuum bubble: voltage level above 6KV-35KV
2. Measuring range: 10
-5
-10
-1
Pa
3. Measurement error: ±10% in 10
-
4
-10
-1
Pa
4. Measurement resolution: 10
-5
Pa
5. The leaking arc extinguishing chamber will undergo electrical breakdown during the
measurement, and the machine is in a protected state.
6. Allowable ambient temperature: -20
℃
-50
℃
, if the test is below 0
℃
, please power on
