Is there a 4-20mA signal amplifier?
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Under the current conditions, the pressure range at the field device is 0–2 MPa, while that at the upper-level controller is 0–1 MPa. When the actual pressure reaches 1 MPa, the upper-level controller displays 0.5 MPa and the current is 12 mA. To achieve the desired outcome, without making any changes to the instruments or the upper-level controller, it is possible to use additional conversion modules or other hardware so that when the actual pressure is 1 MPa, the upper-level controller outputs 20 mA and displays 1 MPa. I’m not sure if I’ve made myself clear; due to various reasons on site, it’s not possible to make any changes to the instruments or the upper-level system. I wonder if there is such a thing – what is it called? Thank you!
The range of the host computer should be consistent with that of the transmitter.
Yes, that’s right. For various reasons, it’s not possible to make any changes to either the host computer or the instruments at the moment. So I’m thinking of trying to use some external devices to achieve this goal – are there any such devices available?
No one does it like you do; actually, what you should change most is the range of the host computer. With your way of making changes, how will it display values at 1.5 MPa?
Mm-hmm, I can’t move either way right now; I don’t know what this is supposed to do. The maximum pressure reaches 1000 – is that possible?
#Let’s quickly review* complex numbers here#
That’s easy; write a note*2 on the space above it.....
Just take an interface, connect it to the transmitter, and adjust the range accordingly; or go to the control room to adjust the range on the display. These are all solutions that don’t require any cost. Yet your company insists on spending money on them – I really don’t know what your managers are thinking
This post was last edited by iam*aoye on 2016-9-26 23:12. In fact, the relationship between the current before and after the transformation is: Y = 4 + (X – 4) * 2, where Y represents the current after the transformation and X represents the original current. The original current is combined with a 250-ohm resistor to convert it into a 1–5V signal, which is then fed into the ADC pin of the microcontroller. As intended by the questioner, the host computer can display a maximum of 1 MPa, which is half of the range of the pressure transmitter; therefore, the value of X ranges from 4 to 12 mA, corresponding to an input voltage of 1 to 3 V for the MCU’s ADC pin. According to the current relationship formula, this is equivalent to the voltage conversion relationship Yu = 1 + (Xu – 1) * 2. Here, Yu represents the output voltage from the microcontroller’s DAC pin, while Xu represents the input voltage from the microcontroller’s ADC pin. It can be seen that as Xu varies between 1 and 3 V, Yu varies correspondingly between 1 and 5 V. By connecting a 1–5V to 4–20mA transmitter to the DAC pin of the microcontroller, the idea proposed by the questioner can be realized. It is worth noting that the current sinking capacity of microcontroller pins is limited; excessive current can easily damage the microcontroller. Most microcontrollers these days can handle currents of several dozen mA, and 20 mA generally will not damage the ADC pins of a microcontroller. At the same time, the microcontroller and the pressure transmitter must share a common ground.