How to measure AC DC Current

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5 Channel Current Transducer Sensor Board

This 5 Channel Current sensor board can measure current AC or DC or PWM (up to 333kHz). It puts out a signal that is directly proportional to the current being monitored. Take a look at this graph to see how the sensor behaves.

In the above chart shows the output voltage of the sensor on the horizontal axis which is what you get when you measure the sensor output. The vertical axis shows the corresponding current measured flowing through your wire of your sensor.

Note: The most common question is about monitoring AC. If the current being monitored is an AC current, then the sensor will put out an AC signal.

Applications for this 5 Channel Current Monitoring Board include monitoring alternative energy, Industrial current monitoring, and for the home hobbyist who has projects brewing in the garage.

This hall effect current transducer board is easy to use with a data acquisition system such as "LabVIEW" or LabJACK USB data logger. It can also be used with a simple hand held volt meter or oscilloscope. This 5 Channel hall effect board can be mounted easily into an electrical enclosure combiner box to monitor your solar panels and wind turbines.

It also is great for laboratory research and development applications. There are 5 separate current sensors that output 5 independent signals. Each signal has its own offset and gain setting that you can adjust to your liking. The output terminals on this board connect easily to data loggers or data acquisition equipment made by companies like Tektronix, National Instruments LabVIEW, or LabJACK.

You can monitor between -72 to 72 Amps of current, AC or DC. When the gain is at it's minimal setting, you will see about 36mV output for every Amp of current detected by the sensor. If your signal is too weak, then simply loop your wire through the sensor 10 times to increase the signal strength by 10x. Or simply adjust the gain adjustment to its maximum value of 10 X. The output range of this board is about -7 Volts to +7 Volts. When monitoring AC current, then the output from this sensor will be an AC signal with a response time of 3 µ sec. The product is firmly mounted on a 1/8" aluminum plate that has 4 mounting screws.

DESCRIPTION

PRICE

Model H5-ACDC-70-MK

5 Channel ±72 AMP HALL EFFECT AC/DC CURRENT SENSOR WITH GAIN & OFFSET

MK = (Includes Aluminum Plate Mounting Kit)

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DATA SHEET

Wiring Example of two H5B-ACDC-70 Current Monitoring Boards. Wired to the labJACK data acquisition box HERE

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Includes 12V wall transformer & Mounting Kit

SATISFACTION GUARANTEED

DELIVERY TIMES: 2 to 5 Days within US, 2 to 3 Weeks World Wide

Also Offered on Amazon.com

3D MODELS AVAILABLE

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h-acdc.IGS

SLDASM Solid Works Model Version 2011

ORDER OPTIONS

MODELS	H5-ACDC-70	H5B-ACDC-70
CURRENT RANGE (Amps)	±72	±72
SENSITIVITY (mV Per Amp Output)	~41mV (For gain adjusted to 1x) ~410mV (For Gain adjusted to 10x)	Fixed: ~ 27mV @12VDC Input Excitation Voltage
ABSOLUTE MAX VOLTAGE OUTPUT RANGE	-8.3V to +8.3	4.060 to 7.940Volts @12VDC Input Excitation Voltage
PWR REQUIREMENTS	12V – 20V DC, < 10W, 2.5mm ID Power Connector
RESPONSE TIME	3 µ sec (333 kHz)

MAX CABLE DIAMETER: 0.43"

This 5 channel current monitoring board lets you adjust DC offset and gain. Provides high current AC or DC measurements to your data logger or volt meter
Linear response.
Works great with a 12 channel LabJACK U3 data acquisition box sold separately - The LabJACK U3 comes with free USB O-Scope / data logger software for your computer to measure and record current or voltage. The LabJACK can be used with three of these boards to monitor 12 current values at once.

MEASURING DC AMPS:

For example, if your data logger has a voltage input range of 0 to 5 Volts and the max DC current you are expecting to see is 50 Amps, then you would adjust your V offset so your output is at zero volts when there is no current flowing through the wire. Next you would adjust your gain so that at 50 Amps DC, your sensor puts out 5 volts. There are two ways to accomplish this. (1) If you have a DC power supply that can put out 50 Amps of current, then turn it on at 50 Amps, and adjust your gain for each sensor so that your dc volt meter reads 5 Volts for each sensor. You can follow these steps:

STEPS TO ADJUST GAIN WHEN NO CONSTANT CALIBRATED CURRENT SUPPLY EXISTS

Why would you want to do this adjustment? ANSWER: TO get the highest resolution from your data acquisition system or data logger.

STEP	DESCRIPTION
1	Set a volt meter to read DC voltage. Use a small screw driver to loosen the screws shown at G and 1. Insert the probes for your volt meter into the terminals as shown. These output terminals correspond to CS1 as marked on the board. (CS1 means “Current Sensor 1”)
2	Next make sure that you adjust the gain potentiometer to its furthest most counter clockwise position. The 22 turn potentiometer shown here is labeled G1. This corresponds to current sensor 1. One way to tell you have reached the furthest most position of the potentiometer is that you will hear a small clicking noise as the wiper runs off the end of the resistor coil. You will also know if your DC Volt reading stops decreasing. By adjusting the gain resistor to this position, you have essentially adjusted gain to its smallest setting of 1X.
3	If you have the model H5-ACDC-70, then adjust the V Offset potentiometer so that your DC volt meter reads ~0.041mV DC. If you have the model H5-ACDC-125 then set your offset voltage at ~0.024mV DC. For instance if you want to adjust the channel 1 current sensor Voltage offset, then you would adjust VR1 as shown in the photo. NOTE: At this point have fooled the amplifier circuit into thinking that the current sensor is reading one Amp of current.
4	No you need to use this formula to figure out what your gain should be. 0.041V x G X 72A = 5 Volts. Solving for “G” you get a gain of 1.7 So now with your volt meter reading ~0.041, adjust the gain on your potentiometer until your DC voltage reads 1.7 X 0.041 = 0.069VDC. This gain value will make it so that your sensor will put out 5 Volts when it sees a 50 Amp Current.
5	Now return your offset to zero using the VR potentiometer. This completes the setup steps for measuring a DC current of 50 Amps max.

Check out a site like this one: p; p; p; p; p; http://www.doctronics.co.uk/voltage.htm

MEASURING AC:

If you want to measure 50 Amps AC, and your data logger has a 0 to 10 Volt input range, then you would adjust your offset so that it sits at 5 Volts, and your gain so that the signal will hit 10 Volts at 50 Amps and 0 Volts at -50 Amps.

If your data logger has a -5 to +5 voltage input range, then you would adjust the offset to zero volts to read an AC signal. Also if your signal is week, then loop the wire around the sensor multiple times and adjust the gain to its max setting.

SOLAR CHARGING APPLICATION - EXAMPLE DATA FROM SENSOR

Below you can see real data from just one sensor for a solar panel / battery charging application. The green trend line represents data from the sensor. The red trend line has been converted to Amps using the following linear equation. (Vsensor - 4.0) / ~32mV

In this case, the offset as left at 4 volts DC. And the gain is set to 1. As the sun comes up, current slowly flows into the batteries rising from 4 Volts DC to 4.5V DC. This corresponds to a current range of Zero amps up to 16 Amps shown in red on the right side of the graph.

When someone in the home turns on an electric appliance then the current goes negative down to 2.6 Volts DC because it changes direction as it flows from the batteries into the House AC inverter which could be powering something like a refrigerator or washing machine. A value of 2.6 Volts DC output converts to a current value of ~ -45 Amps. Assuming these batteries are setup in a 24 Volt configuration, then you could use this current measurement to approximate how much power your batteries are putting out. In this case it would be about 1,080 Watt power output to the inverter.

(24V X 45A = 1080 Watts)

Below you can see a typical application for data logging monitoring the current sensor data. In this case the hall effect transducer offset was adjusted to zero using the potentiometer. Then the gain potentiometers were are turned to the lowest resistance setting which gives us a gain of ~1.

Next a LabVIEW software program ran while monitoring the Lab Jack U3 data acquisition box as shown below. This box has a USB connection to the computer as shown below. Then 20 Amps of DC current was put through each sensor for a time interval of 10 seconds each. You can see that each sensor responded with a nice square pulse at or around 780mV. This is because the sensors put out about ~37mV per amp.

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The U3-HV LabJACK Data Acquisition USB Box able to monitor up to 12 sensors at one time with adjustable sampling rates over 1,000 samples per second.

Technical Details

4 HV Analog Inputs and 12 Flexible I/O (Digital Input, Digital Output, or LV Analog Input)

Up to 2 Timers (Pulse Counting/Timing, PWM Output, Quadrature Input)

Up to 2 Counters (32-Bits Each)

4 Additional Digital I/O

12-bit Analog Inputs (HV: ±10 V or -10/+20 V, LV: 0-2.4 V or 0-3.6 V, SE or Diff.)

Comes with free LJscope.exe O-scope software program. It's like having your own USB O-scope!! You will be able to data log all your data to your computer hard drive with the free software from Labjack.com!

It also comes with software drivers that you can use to acquire the data like LabVIEW, visual basic, C++ and many more.

$129.00

ORDER HERE: U3-HV From Amazon

THIS DATA CORRESPONDS TO A GAIN SETTING OF 1x (Adjustable using trim pots)

Output From Your Sensor (Volts)	Output Converted to Amps
1.62	-72.7
1.947	-62.7
2.274	-52.7
2.601	-42.7
2.928	-32.7
3.255	-22.7
3.582	-12.7
3.909	-2.7
4.236	7.2
4.563	17.2
4.89	27.2
5.217	37.2
5.544	47.2
5.871	57.2
6.198	67.2

FAQ:

Can this sensor measure negative current and positive current?

ANSWER: Yes it measures negative current as well as positive. The transducer output range can be adjusted to have an offset of 5 Volts DC, so that with no current, the output is 5 Volts, if the sensor were to see -10amps, the voltage would drop down to somewhere near 4.6VDC with Gain set to one. And if it were to see +10 amps, the sensor output would go up to somewhere near 5.4 Volts. Or you could adjust the offset down to zero volts so that if the sensor detects negative current, it will put out a negative voltage proportional to the amount of current it is seeing.

When measuring AC current, does this sensor put out an AC or DC signal.

ANSWER: It puts out an AC signal.

If I am using this with a 24 Volt battery application can I just hook the operating power up to the battery?

ANSWER: Yes, this device can take a 12 to 30 Volts DC power supply to excite the transducer using the black 2.5mm positive center.

How can I monitor current from a PWM (Pulse width modulation) signal?

ANSWER: There are two ways of doing this. First is for you to get a data acquisition box that can sample at least 10 times the frequency of your pulse width modulation. Then you would be able to use software like LabVIEW to integrate the area under the waveform to get an accurate current calculation. The second method would be to put an averaging capacitor on the output of the current sensor with a weak drain to ground like 10k Ohm. You could them calibrate the outuput value using a known good standard like reading the voltage drop across a shunt with an O-scope. Since this sensor has a 3us response time, you will be able to monitor PWM current up to about 300,000Hz . If you need more help with this contact me at support@measure-current.com

What is the absolute maximum current this device can measure?

ANSWER: This board uses high quality CSLA2CD transducers made by Honeywell (datasheet here) It has a max current specification of 72 Amps. If you want to measure more current then that, you could purchase the model CSLA2CF sensor and install them easily on the same board which would get you up to the 120 Amps input range.

How can I use this sensor for low current situations less then one amp?

ANSWER: All you have to do is loop the wire through the sensor multiple times until you get the signal strength you need. Then divide the measurement you are getting by how many loops you have put through the sensor. For example, if you loop your current carrying wire through the sensor 10 times, and you get a measurement of 4.032 and your sensor measures 4.0 when no current is flowing through the transducer, then the approximate current calculation would be :

((4.032 - 4.0)/ 0.033) / 10 = 0.096 Amps or 96mA

ADJUSTABLE GAIN POTENTIOMETERS BELOW

ALLOW YOU TO MAKE THE SIGNAL AS BIG OR SMALL AS YOU WANT FROM 1X to 10X

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