Products > Test Equipment
Siglent SDM3045X mA current measurement - weird behaviour
ahope:
Thanks for the pics Tautech. It is clear that my R407 is damaged.
From your picture it looks like a 1R shunt next to the 0R010 R407 shunt.
I am guessing, but going from the 6A scale to the 0600mA scale it will switch from using R408 to R407 as shunt.
So if R407 is damaged, the shunt value will be off, giving the wrong reading?
I am tempted to try to replace R407. Anyone know exactly what spec/type part I should get from digikey or other distributor?
tautech:
--- Quote from: ahope on November 10, 2018, 10:14:39 am ---Thanks for the pics Tautech. It is clear that my R407 is damaged.
From your picture it looks like a 1R shunt next to the 0R010 R407 shunt.
I am guessing, but going from the 6A scale to the 0600mA scale it will switch from using R408 to R407 as shunt.
So if R407 is damaged, the shunt value will be off, giving the wrong reading?
I am tempted to try to replace R407. Anyone know exactly what spec/type part I should get from digikey or other distributor?
--- End quote ---
First you need to identify the SMD size and then of course to maintain accuracy get a low tolerance/low tempco device.
Here's a chart so you can compare physical measurement:
But hold off on ordering anything just yet until we hear what the factory says.....just in case they are willing to send you a replacement PCB.
ahope:
thanks a lot.
i will take good time before replacing this shunt. its a precision part, so I want to make sure I make a good replacement if I have to.
Rough measurements puts it at 6.5x3.5mm or thereabouts. The «F» indicates a 1% tolerance part. But I have no idea if it is a 1w, 2w or something else.
tautech:
--- Quote from: ahope on November 10, 2018, 08:30:56 pm ---thanks a lot.
i will take good time before replacing this shunt. its a precision part, so I want to make sure I make a good replacement if I have to.
--- End quote ---
:-+
--- Quote ---Rough measurements puts it at 6.5x3.5mm or thereabouts.
--- End quote ---
= SMD 2312 (imp) or 6032 (metric)
nctnico:
Perhaps it is also a good idea to put two big diodes anti-parallel to the shunt. That is the recommended way to prevent an overcurrent (surge) from damaging a shunt resistor. Also looking at the size of the resistor it doesn't look like it has been properly sized for handling 10A continuously (= 1 Watt of heat dissipation). The resistor may be rated for 1W (or even more) but those ratings are always in ideal circumstances and running the resistor at the absolute maximum temperature. Derating 3 to 4 times is not a bad idea. A through hole current sense resistor made of thick wire is much more forgiving when it comes to abuse compared to an SMT resistor (AFAIK there are SMT current sensing resistors made entirely from metal but these aren't cheap).
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version