EVDL-10A Quartz Oscillator Vacuum Gauge
1.Product overview
EVDL-10A quartz vacuum meter is a vacuum meter with quartz crystal oscillator as sensor. It has a wide range and high precision. The vacuum gauge consists of a regulation and control unit, and the digital tube of the control unit displays the pressure value.
2.Technical specifications
1. Measuring range：5×10-1-105Pa
2. Power Supply：AC 220V,50Hz
3. POWER：7W
4.Chassis dimensions：180mm×80mm×200mm（L*W*D）
5. Cable length 2m
3.Working principle
EVDL-10A quartz vacuum meter is a vacuum meter made by using the characteristics of quartz crystal oscillator resonance impedance and gas pressure. Quartz crystal oscillator in EVDL-10A quartz vacuum gauge is not only a component of oscillator, but also a sensor for measuring gas pressure. Quartz crystal oscillator is installed in aluminum shell to make gauge pipe with diameter of 15.5mm, which can be inserted into the system through the interface. The measuring circuit of resonance impedance is shown in Figure 1：
Figure 1 Resonant impedance measuring circuit
Resonant impedance Z= V AB
VAB is the voltage across the crystal
I is the current flowing through the crystal
Current I flows through resistor R in series with the crystal, and the voltage across the resistor is VBD
∴ I = V BD
Z=V AB R
VAB is approximately equal to the voltage V0 across AC, VBD is approximately equal to the voltage V1 across DC, and the impedance can be calculated from the measured V0, V1 and resistance values. The single-chip microcomputer converts the impedance into a pressure, and the digital tube displays the pressure value.
4.Characteristics of quartz vacuum gauge
The quartz vacuum meter is characterized by small sensor volume. The crystal vibration size of EVDL-10A quartz vacuum meter is 3.2mm × 1.5mm × 0.8mm. In this way, in addition to measuring the gas pressure like other vacuum meters, the vacuum meter can measure the gas pressure of a small volume, such as a 1cm3 size sealed device, and detect the vacuum holding state.
5.EVDL-10A Quartz vacuum gauge installation
The installation of the EVDL-10A quartz vacuum gauge is shown in Figure 2:
The quartz crystal oscillator and the oscillating circuit are placed in the probe. The lead cable is inserted into the socket of the rear panel of the control unit through a 5-pin plug, and the pipe with the diameter of the probe Φ15.5 is inserted into the vacuum system. Plug the power cable into the rear panel socket of the control unit and plug the other end into a power outlet. The power outlet should have a ground wire to ground the control unit chassis. Turn on the power switch and the control unit digital tube displays the pressure value. Digital tube display 3.2 E 2 means the pressure value is 3.2×102Pa.
6.Quartz vacuum gauge calibration
When the ambient temperature changes, the EVDL-10A should be calibrated as follows:
1. Zero point adjustment: After the machine is stable for half an hour, when the pressure is less than 10-3Pa, press the button in the zero hole of the front panel of the control unit with the screwdriver to release it. If the vacuum system does not reach 10-3Pa, the zero button cannot be pressed.
2. Atmospheric regulation: Expose the atmosphere to the regulation, press the button in the atmospheric hole of the front panel of the control unit with a screwdriver to release it.
