I want to measure alternating magnetic fields 50 Hz to 100kHz. I have the Honeywell SS 495 A linear Hall effect sensor and have used it like in the circuit diagram:

circuit diagram.

I could successfully measure a voltage change when bringing a permanent magnet at the proximity of the SS 495 A. But with various resistors at R1 (0, 1K, 10K, 100K, 1M) and various devices (switch mode power supply, magnetic power supply, fan) I couldn't measure any frequencies (FFT at my oscilloscope).

Have I wired something wrong?

  • 4
    \$\begingroup\$ Why do you have an R1 in your circuit at all? Looking at the datasheet, I don't see a need for an R on the ground lead at all. \$\endgroup\$
    – Aaron
    Commented Jun 1, 2020 at 20:30
  • \$\begingroup\$ Where are these frequencies coming from? If you're looking at picking up stray radio stations, the sensor might not be as sensitive as you think. \$\endgroup\$ Commented Jun 1, 2020 at 20:57
  • \$\begingroup\$ Data sheet does not show R1. | Max range is about +/- 600 Gauss. What is your flux range from other devices? | Datasheet does not mention bandwidth. What do you expect and why? |Expect about 0.1 mV/Gauss \$\endgroup\$
    – Russell McMahon
    Commented Jun 1, 2020 at 22:24
  • \$\begingroup\$ REMOVE R1 !!! || Supply current is typically about 7 mA. R1 is improperly used BUT for it to drop say 9V to 5V the max R allowed is R=V/I = (9-5)/ 0.007 =~ 500 Ohms. Anything over 500 Ohms starts to impact operation at 9V and lower at lower V. \$\endgroup\$
    – Russell McMahon
    Commented Jun 1, 2020 at 22:27
  • \$\begingroup\$ "But with... various devices (switch mode power supply, magnetic power supply, fan) I couldn't measure any frequencies" - perhaps because these devices are designed to not radiate massive amounts of EMF? \$\endgroup\$ Commented Jun 2, 2020 at 7:18

1 Answer 1


Have I wired something wrong?

R1 is not required and will cause incorrect or no operation at values of much above 500 Ohms with a 9V supply.

The sensor operates with a "hard" supply on Vs, and will tolerate use of a 9V battery.
Adding a series resistor as you have done shows a misunderstanding of how the device works.

As shown in the data sheet - connect power supply to Vs+ and Vs-and take output from 'Output' and Vs-

enter image description here

The datasheet advise that Vs may be 4.5 to 10.5 volt.
Supply current is 7mA typical and 8.7 mA at Vs = 5 Vdc.
Operation from a 9V battery is acceptable. An Alkaline 9V battery will have an unloaded voltage when new of up to about 10 V absolute maximum, so is still within specification.

If you want a non varying Vs you should use a voltage regulator.
The series resistor will drop V = IR.
With a nominal 9V battery the 4.5V lower limit will be reached when R = V/I = (9-4.5)/ 0.0087A = 517 Ohms.
As the battery voltage falls an even smaller resistor would be required to allow correct operation. With resistors of " ... 1K, 10K, 100K, 1M" the devbice will not function.

  • \$\begingroup\$ I tested 0 Ohm (no resistor) but in all my chaos maybe only at the test series when it was not electrically shielded and I saw only electrical fields. I thought a resistor would increase higher frequency response. \$\endgroup\$ Commented Jun 2, 2020 at 22:45

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