whether you're measuring temperature pressure or flow sensors transmit their measurements to control systems via some form of electrical signal that's why choosing a sensor with the right signal output for your application is so important so let's take a look at the options here are the three most widely used sensor output signals and how they stack up first we'll look at dc voltage dc voltage output sensors use analog voltage to transmit measurements with the most common voltage ranges being 0 to 5 volts dc and 0 to 10 volts dc this diagram shows a dc voltage sensor connected in parallel with the resistors r1 r2 and r3 representing the load caused by each connected device let's call r1 a panel meter r2 a controller an r3 a data logger if we have these devices wired in a parallel circuit with a power supply to provide the excitation voltage to the sensor the voltage generated by the sensor will be equal across each device on the upside a sensor with dc voltage output signal is simple relatively inexpensive and nearly all industrial meters and controllers will accept voltage signals on the downside dc voltage output signals suffer from voltage drop across the length of the cable run which has a direct effect on accuracy and they are susceptible to electromagnetic noise and interference and dc voltage output sensors require three or four wires two for supply or excitation voltage and 2 for output voltage next let's look at the 4 to 20 milliamp current loop this very simple yet robust sensor signal standard converts the sensor's output so that the zero point or low threshold reads 4 milliamps in the system and the highest threshold appears as 20 milliamps this makes troubleshooting very easy since a reading at 0 milliamps will indicate an open circuit or lost feed other advantages include easy wiring and installation since only two wires are needed between the sensor and the receiver they're not affected by electrical noise and since the current level remains the same throughout the loop measurements aren't affected by small voltage drops across other devices on the loop and the only limitation to the number of devices is the amount of voltage from the power supply driving the current loop on the downside each sensor in your system will need its own cable run to the power supply and receiver and each 4 to 20 milliamp loop only sends information one way either to or from the instrument next up let's look at millivolt per volt output signals millivolt per volt or bridge sensor outputs are mainly used in applications where pressure transducers or load cells are being used the name millivolt per volt output refers to the ratio of output voltage to the excitation voltage required for the sensor to work for example a sensor with a nominal rated output of 2 millivolts per volt excited with 5 volts will provide a nominal voltage output of 10 millivolts whereas 10 volts excitation will result in a nominal voltage output of 20 millivolts the upside to millivolt per volt output is low cost fast response times and smaller size the downside is the need for a regulated power supply to provide excitation voltage shorter signal ranges and they're vulnerable to electromagnetic interference so there you have it the three most commonly used sensor output signals still have questions we have answers call or chat online with one of our engineering experts at omega.com thanks for watching and be sure to like and subscribe