Issues with instruments and safety barriers
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We have AI safety barriers on our DCS system. AM1031EX and LeCroy’s analog signals. When not connected, a voltage of 24.8VDC is measured at points 7-8; however, once the ultrasonic level gauge is connected (which operates on a two-wire system with a voltage range of 18-30VDC),… At 1W, the voltage is only around 7.8V, so the screen does not light up; however, if the safety barrier is not connected and the signal is sent directly to the AI card, there is no problem at all. I placed the level gauge next to the DCS cabinet and connected it, but there is still only 7.8V, and the screen does not light up either
It is recommended to check the nameplate of the level gauge to see whether it is intrinsically safe or flameproof. It’s the information marked as Ex*****; maybe information such as voltage and current will also be sent over, so let’s take a look.
This post was last edited by Crazy 丶 on 2019-5-30 at 15:46. Servo motor level gauges or certain types of radar/ultrasonic level gauges are not suitable for intrinsically safe circuits. The load is insufficient; it is recommended to use a barrier or to connect it directly to the AI card. It is also necessary to determine the explosion-proof requirements at the site. If that doesn’t work, reverse it with another table
What you mentioned requires a detailed analysis; first of all, ensure that the wiring is correct, with 24VDC having a positive and a negative pole. Second, you can try using a different safety barrier for the test. Troubleshoot one by one
Powered by 24.8VDC; after connecting the ultrasonic level gauge, 7.8V remains, which means the voltage available for the load (level gauge + safety barrier) is only 24.8-7.8=17V. Without connecting a safety barrier, it is generally sufficient to meet the 18-30VDC power supply requirement of the level gauge. When the safety barrier is connected, it consumes a voltage of around 1V, leaving insufficient voltage for the level gauge. This type of level gauge is two-wire, 18-30VDC. 1W) AI cards powered by 24V should not be used via safety barriers; instead, AI devices with isolation functions should be used directly in connection with the level gauge ； It is powered by an isolation barrier level gauge with a power supply function, along with an AI card that may or may not have a power supply. Most two-wire transmitters require a supply voltage of 12-30V, so this situation does not occur. 18-30VDC, which meets the power supply requirements for two-wire instruments, but does not satisfy the needs of 24V safety barriers.
The load is insufficient; isn’t the safety barrier powered separately?
This post was last edited by 1111111 on 2019-5-30 22:22. 1. The safety barrier itself consumes power, resulting in a voltage drop of around 4V, and this cannot be avoided. 2. Ultrasonic waves – can the minimum operating voltage really reach 18V? Haha, whose gauge is this? To the person who designed the circuit for this gauge, I guess they must have mixed things up with 49205455; their mind must be in such a mess that it doesn’t function properly. :P 3, 18-7.8 = 10.2V. Well, no matter how difficult it is, I still have to come up with a solution for you so that you can get this faulty watch working again: ① Use a 28VDC aviation power supply in order to increase the excitation voltage. Use a power supply of 30VDC or higher with caution, unless you understand the circuit board and are aware of the voltage tolerance values of the relevant components. ②Replace the circuit board with one that uses a sampling resistor of around 50Ω. The circuit board you’re using currently likely has a sampling resistor of 250Ω, or even possibly 500Ω! For this ultrasonic skin, the resistance value is extremely high. You can measure the exact resistance value. In case you don’t know how to do the measurement, you can call brother at 13709170262. Points ① and ② mentioned above are intended to ensure that a voltage of at least 10.2V is available, so that the voltage at the terminals connected to the ultrasonic device is higher than 18V. Only by ensuring this can the meter be powered on without any signal distortion. ...... (10,000 words omitted)