Moksadul e-Lab

Human Automation VS Industrial Automation

🔧 Understanding a Compound Pressure Gauge in Industrial Systems

In many industrial process systems, monitoring both positive pressure and negative (vacuum) pressure is essential for safe and stable operation. The instrument shown here is a compound pressure gauge, which can measure pressure above and below atmospheric pressure.

📊 Gauge Range
This gauge has a measurement range of approximately –0.1 MPa to +0.15 MPa:

Negative side (Vacuum): –0.1 MPa

Positive pressure: +0.15 MPa

This allows operators to observe whether the system is operating under vacuum conditions or positive pressure.

*Output : Generally this type of gauge give output relay contact ( NO/ NC) for alarm.

Compound gauges are commonly used in:
Chemical dosing systems
Water treatment plants
Pump suction and discharge monitoring
Filtration systems
Closed tank or pipeline monitoring

💡 Light Dependent Resistor (LDR):
A Light Dependent Resistor (LDR), also called photoresistor, is a special type of resistor whose resistance changes automatically with the intensity of light falling on it.

An LDR is a passive electronic sensor that detects light.
📌 More light → Lower resistance
📌 Less light (darkness) → Higher resistance

Working Principle
The working of an LDR is based on the principle of photoconductivity. When light photons hit the semiconductor surface, they release electrons. More free electrons mean better conductivity.
So, the resistance decreases as light intensity increase

🌍 Common Applications of LDR

✅ Automatic Street Light Control
✅ Solar Garden Lamps
✅ Light Intensity Measurement
✅ Camera Exposure Control
✅ Burglar Alarm Systems
✅ Smart Home Lighting Automation
✅ Day/Night Switching Circuits