How Can We Measure The Draw Of An Entire Circuit - How can we work out the current draw of an entire circuit including all the devices connected to it, taking into account resistance of connections and cabling?
How Can We Measure The Draw Of An Entire Circuit Including All Devices Connected.
How Can We Measure The Draw Of An Entire Circuit – How can we work out the current draw of an entire circuit including all the devices connected to it, taking into account resistance of connections and cabling?
A: Disconnect the positive end of your circuit from the power terminal and connect the ohmmeter or DMM with test leads set for resistance to the circuit ends. You are going to measure total loop resistance across the still attached negative terminal and the disconnected positive lead.
Depending on whether you want to measure devices when idle or active, you may need to ensure switches and sensors are in line when you make this measurement and that may mean bridging sensors or having other techs trip devices at the time you make the reading. It’s easier if you are measuring the circuit when in an idle state but the issue you might be having with say, voltage drop, may only occur when a particular device, or group of devices is active.
The highest resistance value in ohms you observe should be divided into circuit voltage (say, 12.4V DC) to calculate current. Using an ohmmeter, make sure you factor in a floating 0.4 ohm reading with the probes crossed.
This variable can remove as much as 30 per cent of the total value measured in low resistance loops. On a 12-volt circuit with a resistance of just 1 ohm this misinformation can subtract 4 amps from your calculated current draw, which for low voltage circuits is a lot of current.
You can learn more about measuring resistance from the folks at Fluke here or read more SEN news here.
“How Can We Measure The Draw Of An Entire Circuit Including All Devices Connected.”
How Can We Measure The Draw Of An Entire Circuit Including All Devices Connected.
A professional writer and editor who has been covering the security industry since 1991, John is passionate about clever applications of technology and the fusion of sensing and networking. A capable photographer John enjoys undertaking practical reviews of the latest electronic security systems.
