I would like to ask Haiyou 707: which mode should be selected for passive signals?
Thread Content
I would like to ask Haiyou 707: which mode should be selected for passive signals? The card is connected to a three-wire instrument, and now I want to use a 707 signal generator to supply a passive mA signal directly to the terminals. I would like to ask fellow users which mode of the 707 should be selected? Personally, I think the milliampere output mode should be chosen, but another guy said that the analog milliampere mode should be used; there’s a difference between the two, so I’m asking the other users here for their opinions. See attached figure
As you said, it sends a passive mA signal, using the analog milliampere mode
The reason I chose the milliampere output mode is that in the diagram in the manual illustrating the milliampere mode, a power supply was shown connected, meaning the signal it outputs is voltage-driven and active.
It has been tested in practice, and I’m here to report on it so that other users facing similar issues can refer to it. The card model is 1756-IF16; it is used to connect to three-wire combustible gas sensors, with the sensor outputting a signal of 4~20mA. Wiring terminals: 1, 24VDC+ ； 2. Probe output signal ； 3. First disconnect terminal 1 of the COM, then connect terminals 2 and 3 using a 707 device. Set it to analog milliampere mode; the 707 will display an open circuit symbol (OL). As the mA value is increased on the 707, the value on the screen does not change. Next, the milliampere output mode of 707 is selected; the OL symbol for an open circuit is not displayed on 707, and 0.0 can be seen on the screen. As the mA value increases on 707, the numerical value on the screen rises as well, and an alarm will be displayed when the set point is reached.
The second mode is when the circuit does not require a 24VDC power supply
Active or passive? It depends on the diagram: the signal in the left diagram is passive, while the signal in the right diagram is active. The right diagram indicates that this gauge functions like a two-wire 4–20mA transmitter – you need a 24VDC power supply to supply power to it, so that it can output current. . . If you don’t supply power, it will act like a dead dog; it won’t deliver any current for you to use. . . . . . But then again, for circuit boards, when the power supply used is not provided by the board itself, the board claims that the signal is an “active signal”; whereas when the power supply is provided by the board, it claims that the signal is a “passive signal”. So, the concept of whether a 4–20mA two-wire signal is active or passive is nothing but nonsense, a made-up idea with no basis in reality. . . When it comes to the card itself, it’s simply a “two-wire active card” or a “passive card” – that’s all there is to it! , What’s the point of using pulling signals for...? It’s a case of misattribution
The wording in the instructions is not good; changing “analog mA” to “analog two-wire 4–20mA transmitter” will make it easier for everyone to understand.
This is still pretty good; I’ve learned * from it