I am working with automation using pH and EC sensors. Both are of 4-20mA communication standard. When at a time single sensor is placed in liquid(in 1000 litre tank) then everything works fine (correct value is given). But when both sensors are placed in liquid and reading is taken simultaneously from both sensors then value is unacceptable (large variation as compared to actual result). Both sensors are supplied power (24V DC) from single point and also grounded at common point. What is wrong when both sensors are placed in same liquid ?

  • \$\begingroup\$ pH and EC sensors should not interfere each other.There are many possibilities. Perhaps the PSU is overloaded. To verify this try: (1) Use 2 PSUs' one for each sensor, testing at 2 separate points, without shorting both grounds. \$\endgroup\$
    – tlfong01
    Nov 4, 2020 at 7:28
  • 1
    \$\begingroup\$ @tlfong01, I have switch ON pH sensor at a time keeping EC sensor OFF. Then after some delay switch ON EC sensor keeping pH sensor OFF. This works for me. \$\endgroup\$ Nov 17, 2020 at 7:14
  • \$\begingroup\$ I am glad to hear the good news. So perhaps both the devices have a big starting current, and the solution is not to start both at the same time. Have a nice project. Cheers. \$\endgroup\$
    – tlfong01
    Nov 17, 2020 at 7:21


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