请问有适合PS203和开发包CY8CKIT-030直接测量20mA的电流吗？

最简单的方法是让20Ma流过电阻（分流器），测量电压，然后使PSoC3与ADC数字化。用欧姆定律计算所需的分流器和所需的最大电压。
Dana WIL可能建议您根据您的结果所需的精度对设计进行错误计算。
鲍勃



以下为原文
Easiest would be to let the 20mA flow through a resistor (shunt) and measure the voltage across and then have the PSoC3 digitize that with the ADC. Calculate with Ohm's law the needed shunt and the needed max. voltage across.
Dana wil probably advise you to make an error-calculation for your design based on the precision you need for your results...

Bob

谢谢你的回复。
我想知道目前的0~20mA是否可以直接注入PSoC，然后在没有外部成分和TIA或其他东西的情况下测量，但显然是不可能的。
西尔万



以下为原文
Thanks for your replies.
I wondered if the current 0-20mA could be injected directly into the PSoC and then measured without external component and with a TIA or other things but apparently it is impossible.
Sylvain

TIA没有足够低的R值来处理20毫安。
你可以看看把电流注入到输出引脚驱动的低电平，
进入MOSFET输出饱和区。但问题是
RDSON的设备到设备的变化。如果你做了一个生产CAL
生产测试，然后你可以纠正这种变化。模数转换器
用于引脚测量电压，因此计算电流为基础
关于RDSON的测量V和知识。
另一个问题是像这样使用的PIN的顺应范围。
VDIO+.5V。
问候，Dana。



以下为原文
The TIA does not have a low enough value R to handle 20 mA.

You could take a look at injecting current into an output pin driven low,
into saturation region of MOSFET output. But problem with this is
device to device variation of Rdson. If you did a production cal at
production test then you could correct for this variability. A/D would
be used on pin to measure voltage, hence compute current based
on measured V and knowlege of Rdson.

Another issue is complience range of a pin used like this would be
Vddio + .5V.

Regards, Dana.

源4-20MA允许在电路中包含低电阻电阻器。鲍伯建议使用分流器。我喜欢下面的图像。当然，没有电隔离。
20M.PNG
33.8 K



以下为原文
Sources 4-20 mA allow the inclusion of low-resistance resistor in the circuit.
Bob suggested the use of a shunt. I do like the image below.
Of course there is no galvanic isolation.

• 20mA.png33.8 K
  
  

一些问题
1）这是一个4/20毫安的电流回路还是只是一个单端电流源下沉到地面？
2）电流源双极或单？
3）范围为0～20 mA或4～20 mA？
4）你想测量负载或接地侧的热电流吗？
5）你想要达到的准确度（绝对值）？
6）电流测量的分辨率？
7）待测样品率？
8）电流源DC或包含大量噪声？
9）源提供的绝对最大峰值电流？
问候，Dana。



以下为原文
Some questions -

1) Is this a 4/20 mA current loop or just a single ended current source sinking to ground ?
2) Current source bipolar or mono ?
3) Range is 0 - 20 mA or 4 - 20 mA ?
4) You want to measure current in hot side of load or ground side ?
5) Accuracy (absolute) you are trying to achive ?
6) Resolution of current measurment ?
7) Sample rate of measurements to be made ?
8) Current source DC or comprising a lot of noise ?
9) Absolute max peak current provided by source ?

Regards, Dana.

用TIA的解决方案不合适。这是因为您正在用外部设置G。
R，从而将TIA转换为V放大器。原因是芯片20K TIA R，最有可能，
一个可怕的绝对值，根据DS的60%。而是使用PGA，其中G是F（R/R），
与之对应的R片的片上精度相当好，参见PGA的G规格，最高G 5%。
g精度。
注A/D有一个G可编程输入缓冲器，1, 2, 4，8克的可用。如果需要更多的G
使用PGA。
问候，Dana。



以下为原文
The solution with TIA not appropriate. This is because you are settting G with external
R, thereby converting TIA to V amplifier. Reason is the onchip 20K TIA R has, most likely,
a horrible absolute value, 60% according to DS. Rather use a PGA, where G is a f( R/R ),
and onchip accuracies of ratioed R's is quite good, see G spec for PGA, at highest G 5%
G accuracy.

Note A/D has a G programmable input buffer, 1, 2 , 4 , 8 G's are available. If more G needed
use PGA.

Regards, Dana.

这可能有助于，附加，如果电流循环…
问候，Dana。
40-3407.PDF
517.4 K



以下为原文
This may help, attached, if current loop....

Regards, Dana.

• 40-33407.pdf517.4 K