SensingBench electronicsSpecialist reuse
Pressure sensor
Also called BMP, blood pressure sensor, MPX.
The transducer in a blood-pressure monitor or a weather gadget, as opposed to a switch. Often a small ported package plus an amplifier. Without the part number it is an analog voltage you can calibrate, not a known kPa/V.
If you are new to this category
A sensor reports a condition such as weight, light, temperature, or position. Many sensors do not switch fully on or off. A kitchen scale bar, for example, changes by thousandths of a volt. Keep the small board that read the sensor if you still have it.
Keep the connector. Write down the wire colors before you cut them. If you do not know which wire is which, the sensor is hard to reuse.
Red and black feed the sensor a steady few volts. Green and white are the tiny signal, measured between them, not from either one to ground. Pressing the bar changes that signal by millivolts. A normal meter on DC volts can show that it responds. Turning it into a number on a screen wants a small amplifier board, often an HX711.
| What to look for | Usual figure |
|---|---|
| BP cuff | Range covers roughly 0–300 mmHg. The hose port and the board it is on are the usable unit. |
| Digital | Some boards are I²C barometers. Those are reusable if you can read the chip marking. |
Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.
What people actually use it for
- A cuff project
- A relative pressure reading you calibrate yourself
Leave this one when
The port is clogged with gel or the chip is unmarked and you needed absolute accuracy.
Buying a new one is the better idea when
A labeled sensor. Pressure parts are not expensive compared to a wrong reading.
How to tell if this one still works
Power the original board and watch the output voltage change when you apply a gentle breath. Do not exceed what a cuff would have done.
Tools you will want: Meter, The original board.
Where people actually find it
1 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.
| From | Call | How many | How often | Where it sits |
|---|---|---|---|---|
| Blood-pressure monitor | Worth it | 1 | usually | On the board, with a port. |
- In this particular machine
- Analog, cuff range. Calibrate it.
- Where to look
- On the board, with a port.
- How to get it out
- Keep it on the board.
- The condition to expect
- May be the fault.