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我使用一个∑ΔADC的读数作为PID回路的控制变量。它在基于FET的电流源中读出读出电阻。FET上的栅极电压是过程变量。
当我把电压输入ADC时,我得到准确的读数。然而,一旦我在电路中包括FET和电流感应电阻,我就得到虚假的读数。系统的输出是稳定的,它只是在错误的电流。ADC读取控制变量的值等于或接近设定点,但我的实际输出高达200%。 我已经玩了几天了,我想不出来。这个项目是附加的…如果有人能给我任何洞察力,我将非常感激。 迈克 可变负载 3.1兆字节 以上来自于百度翻译 以下为原文 I'm using readings from a Sigma Delta ADC as the control variable for a PID loop. It's reading across the sense resistor in a FET based current source. The gate voltage on the FET is process variable. When I just feed a voltage into the ADC, I get accurate readings. However, as soon as I include the FET and current sense resistor in the circuit, I get bogus readings. The output of the system is stable, it's just at the wrong current. The ADC reads the control variable's value as equal to, or close to, the setpoint, but my actual output is off by as much as 200%. I've been playing with this for a couple of days and I can't figure it out. The project is attached...If anyone can give me any insight into this, I'd be much obliged. Mike
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2个回答
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我远离计算机,不能检查原理图,但我怀疑FET电路有噪声拾取,特别是如果PWM控制的话。我建议添加小帽子来滤除噪音。检查输入信号的范围。
奥迪赛1 以上来自于百度翻译 以下为原文 I am away from computer and can't inspect the schematic, but I suspect there is noise pickup from the FET circuit, particularly if it PWM-controlled. I would recommend adding small cap to filter out noise. Check incoming signal with scope. odissey1 |
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nvwuwy 发表于 2018-12-26 10:23 不坏的想法,但我不认为这是一个噪音问题。我用电池作为FET电路的电源,尽量减少电路中的噪声,但没有效果。 在电流感应电阻和输入电源之间增加100NF根本没有帮助这种情况。 什么* *帮助重新分配ADC引脚从哪里到另一个引脚。我不明白为什么这是可能的,但是一旦我把ADC从PIN 0.4变为0.2,问题似乎已经解决了。我想知道这是否与我使用运算放大器2的事实有关,P0.4与OA2的非反相输入有关。理论上,运算放大器应该内部断开,但实际上,也许不是。或者,在非反相输入端的信号中可能会有一些噪声流过?我不知道。 以上来自于百度翻译 以下为原文 Not a bad thought, but I don't think this is a noise issue. I've used a battery as the power supply to the FET circuit to try and minimize the noise in that circuit but to no avail. Adding 100nF across the current sense resistor and across the input supply did nothing at all to help the situation. What *did* help was reassigning the ADC pin from where it was to another pin. I'll not get into why that was possible, but as soon as I changed the ADC from being on pin 0.4 to 0.2 the problem seems to have resolved. I'm wondering if that is somehow related to the fact that I'm using op-amp 2, and P0.4 is tied to the non-inverting input of OA2? Theoretically, the op-amp should be internally disconnected but practically, perhaps it wasn't? Or perhaps some noise bleeds across from the signal on the non-inverting input? I don't know. |
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