BM235 400 mA fuse question

[rcbuck]

I blew the 400 mA fuse in my EEVblog meter. I accidentally put it across a 12 volt, 1/2 amp power source. One pin off on the connector.

I have found several HRC fuses rated at 500 mA. That would be an acceptable replacement instead for the 400 mA original.

The question I have is does the internal resistance of the fuse have any affect on the current measurement? The fuses I have found vary from 0.5 ohms to 3.5 ohms. I'm tempted to replace it with a standard 3AG fast-blow fuse as the highest voltage I ever measure is about 40 volts.

Could someone please measure the resistance of the original fuse and post the result here? That would give me an idea of which replacement to buy. The SIBA fuses are unobtainium in the U.S. as far as I can tell. Amazon and Ebay have them but I wouldn't trust either one of those sources.

Thanks.

[Yansi]

SIBA can be probably bought from TME.eu, even in the US of A.

[Fungus]

I'm fairly sure you can buy fuses from the same place you bought the meter from...

[ComradeXavier]

The question I have is does the internal resistance of the fuse have any affect on the current measurement? The fuses I have found vary from 0.5 ohms to 3.5 ohms.

I am not a measurement expert, but I wouldn’t expect the resistance of the fuse to affect the voltage drop across the meter’s current shunt in any significant way.

Could someone please measure the resistance of the original fuse and post the result here? That would give me an idea of which replacement to buy. The SIBA fuses are unobtainium in the U.S. as far as I can tell. Amazon and Ebay have them but I wouldn't trust either one of those sources.

I can’t measure the original because I also popped mine. I found and bought a comparable replacement from DigiKey. Not cheap, but I wanted to meet the markings on the meter so I won’t surprise myself later.

[Fungus]

The question I have is does the internal resistance of the fuse have any affect on the current measurement? The fuses I have found vary from 0.5 ohms to 3.5 ohms.

I am not a measurement expert, but I wouldn’t expect the resistance of the fuse to affect the voltage drop across the meter’s current shunt in any significant way.

No, it won't...

...but 3.5 Ohms might add significantly to the burden voltage of the meter and affect readings that way. I'd go for the lowest Ohms.

[rcbuck]

I bought the meter from Amazon but would not trust Amazon for the fuses.

I'll just buy the one from Mouser that has the 2.9 ohm resistance.

Edit: Actually the Mouser part has 0.587 ohms resistance.

[jancumps]

they are for sale on the EEVblog shop: https://www.eevblog.com/product/multimeter-fuse-pack/

[J-R]

What I've got:

BM235 - SIBA 400mA 1000V: 1.33 Ohms

121GW - ASTM 400mA 600V: 1.89 Ohms

ASTM 400mA 1000V fuse pack from Dave's shop:
1.80
1.89
1.79
1.74
1.79

Total resistance on my BM235 is near zero in the 10A range, 2.35 Ohms in the mA range and about 100 Ohms in the uA range.