Sensîr Gerav: Prinsîp Karkirina, Tîp & Wêne Sîstemî
Voltage Sensor çi ye?
Voltage sensor di bir sensor e ku biyanin da pîvanên voltageyê an jî nîşan bide. Voltage sensors dikarin pîvana AC voltage an DC voltage taybet bike. Input i vê sensora voltage ye, wate output i switches, analog voltage signal, current signal, an audible signal dibit.
Sensors divê wan device yên ku biyanin an jî reaksiyên bi electrical an optical signals bikin. Implementasyon a voltage sensor an jî current sensor teknik û şertan de wek biryarên mir bi metodên çawn conventional current an voltage measurement hene.
Di navbera vê article de, dikarin derbarê voltage sensor li ser detail bisede. Voltage sensor dikare pîvan, monitor, an jî measurement da supply ya voltage bigere. Dikare pîvan AC level an/ve DC voltage level bide. Input i voltage sensor voltage yekar e, wate output i analog voltage signals, switches, audible signals, analog current levels, frequency, an jî frequency-modulated outputs dibit.
Yani, hîn voltage sensors dikarin sine or pulse trains ji bo output werin, an jî hîn dikarin amplitude modulation, pulse width modulation, an jî frequency modulation outputs bigirin.
Di voltage sensors de, measurement li ser voltage divider base dike. Du cûrî voltage sensors hene: capacitive type voltage sensor an jî resistive type voltage sensor.
Capacitive Voltage Sensor
Dikarin bînin ku capacitor du conductor (an jî du plate) hate, li navbera wan non-conductor nehatiye.
Non-conducting material wê dielectric name kir. Jeger AC voltage li ser wan plates bidibandin, current dikare dest pê bike bi rêjiya attraction an repulsion elektronan via opposite plate's voltage.
Field li navbera plates dikare complete AC circuit bikin bêtir hardware connection. Ev ji bo capacitor re kame.
Deriyê, dikarin voltage division di du capacitors de ku li ser series ne berdewam bikin. Herdu, di series circuits de, high voltage dikare develop bikin li ser component ku high impedance heta. Di case capacitors de, capacitance an impedance (capacitive reactance) herdem hatine inversely proportional.
Relation between voltage and capacitance is
Q → Charge (Coulomb)
C → Capacitance (Farad)
XC → Capacitive reactance (Ω)
f → Frequency (Hertz)
From the above two relations, we can clearly state that the highest voltage will accumulate across the smallest capacitor. The capacitor voltage sensors work based on this simple principle. Consider we are holding the sensor and then placing its tip near a live conductor.
Here, we are inserting the sensing element of high impedance into a series capacitive coupling circuit.
Presently, the sensor’s tip is the smallest capacitor coupled to the live voltage. Thus, the whole voltage will develop across the sensing circuit, which can detect voltage, and the light or buzzer indicator is turned on—this is behind the non-contact voltage sensors you use at home.
Resistive Voltage Sensor
Two ways exist to convert the resistance of the sensing element to the voltage. The first one is the simplest method, which is to provide a voltage to the resistor divider circuit comprised of a sensor and a reference resistor, which is represented below.
The voltage developed across the reference resistor or sensor is buffered and then given to the amplifier. The sensor’s output voltage can be expressed as
This circuit’s drawback is that the amplifier present will amplify the whole voltage developed across the sensor. However, it is better to amplify only the voltage change due to the change in the sensor’s resistance, which is achieved by the second method implementing the resistance bridge, as shown below.
Here, the output voltage is
When R1 = R, then the output voltage becomes approximately
A → Gain of instrumentation amplifier
δ → Change in the resistance of the sensor, which is analogous to some physical action
In this equation, the gain must be set high because only the voltage change due to the change in the sensor’s resistance is being amplified.
