Page 17: of Marine Technology Magazine (November 2025)

These include thermocouples, photovoltaic, and piezoelectric.

Passive transducers produce a change in resistance (potenti- ometer, strain gauge, thermistors, reed switch), capacitance (gauges), or inductance (differential transformer) as the re- sponse to a change in a parameter.

A sensor detects a speci? c physical, chemical or biological quantity and converts the value it receives into an electrical signal. Sensors require an ampli? er as they are limited to sig- nal level power, often less than 1W. They cannot pass a great deal of power themselves. For power management, use a sen- sor to control an ampli? er circuit: a relay, transistor, optocou- pler, or MOSFET.

Reed switch

One of the originals: a reed switch is a magnetically acti- vated switch. It opens or closes depending on the presence or absence of a magnetic ? eld. Because they can’t handle much current, it’s important to think of a reed switch more as a mag-

Figure 4 netic sensor than a switch. They are commonly available as

SPST and SPDT. They come in a variety of sizes. Smaller

Schematic of the 6-pin TI LM3880 Simple Power Supply units are more sensitive to magnetic ? elds, but carry the least

Sequencer. (Cost: $1.02) (Photo: Texas Instruments) power. Reed switches have small leakage currents compared

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