Comment summary #38
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Comment 371 ... 380
| date | article | author | comment |
| 09 jul 2015 19:25:10 | Accuracy, precision & resolution | John McGaughey | In the example shown for total measurement uncertainty I believe the sum of 3.5 V and 3.0 V is 6.5 V , not 7.5 V. |
| 11 jun 2015 12:05:16 | Shunt resistors | Freddy | The shunt resistance can be calculated with equation 1. If the current through the measuring instrument is neglectable, the shunt resistance is 0.05V/5A=0.01Ω. The power dissipation is very small: 0.05V*5A=0.25W. When using constantine, and using a reasonable length (0.2m) of wire the cross sectional area will be 0.2m*490*10^-9Ω*m/0.01Ω=9.8mm^2. In practice this means you have to use a flat stip wire. |
| 10 jun 2015 14:30:41 | Shunt resistors | Milan Dave | Hi I have seen your Shunts Resistors Page. it was very informative. but i have some doubts which i need to clarify. if i want to make 5 amp DC Shunts only for project work with 50millivolt then 1) What will be the resistance of the shunts. (How to calculate it) 2) after calculating shunts resistance in your example,you took constantin wire of .5mm and putting the formula you said that it will require 0.4m in lenght,but will 0.4m long wire will sustain that much amount of current. ( what will be the current carring capacity of the wire) i have that doubt, i will be very much happy if you clarify my doubts with an example that you are making for example 5amp dc shunts with 50mv. |
| 08 jun 2015 23:45:25 | Arduino: Analog measurements | Freddy | Disabling the digital inputs is not required, but is reduses the power consumption a little bit. It was a remnant from earlier test. |
| 04 jun 2015 14:13:16 | Arduino: Analog measurements | Anmol | Any specific reason for disabling the digital inputs, will the free running mode work without disabling them? |
| 09 mei 2015 13:27:12 | New wattmeter project | Freddy | Thanks for the suggestion. The plan is to implement a FFT functionality to do power and amplitude spectrum analysis. So, a THD measurement is therefore easy to implement. A little update: An ARM Cortex STM32F407 is chosen as main controller. The power consumption is very low, has enough internal memory and it has a floating point unit to do all the math work. |
| 09 mei 2015 13:11:01 | Arduino wattmeter | Freddy | This question is outside the scope of this article. But look at DC-DC converters with you components supplier. |
| 07 mei 2015 18:25:24 | New wattmeter project | Ragothamann R. | Congrats for the wonderful project, I suggest you to add THD % (Total Harmonic Distortion) measurement also included with this. |
| 07 mei 2015 12:42:18 | Arduino wattmeter | salim | Not for the arduino i am using another signal conditioning circuit then i need negative Vcc for the op amp but i wanna use only one battery of 12 v how can i get this neative voltage ?? |
| 07 mei 2015 02:24:38 | Arduino wattmeter | Freddy | The Arduino Wattmeter doesn't need a negative voltage. If you want to use a negative 12 volt for testing than connect the positive terminal of the battery to "COM" and the negative terminal to "V". The wattmeter shows a negative voltage reading of the battery. |