Diode testing question

[semanticart]

Newbie questions here -- I tried searching but couldn't find an answer specific enough.

I'm building an ergodox and soldering on the 1N4148W-FDICT-ND surface-mount diodes. After soldering the first diode I decided to test it with a mutlimeter. I got a value of 0.920MΩ. The second diode tests at 0.873MΩ.

At first I thought the difference might indicate poor soldering but then I tested two different unsoldered diodes and they consistently yielded 0.860MΩ and 0.902MΩ.

Is this variation normal or something I should worry about? Is my cheap Radioshack multimeter to blame? What should I really be looking for when I test my mounted diodes with a multimeter?

[hasu]

Doesn't your multimeter have diode test mode? My cheapest DMM even has that mode, I think yours does.

I measured my axial 1N4148 in diode test mode and resistance mode; Vf :0.6V and 265KOhm.
Though, I'm not sure how diode soldered in PCB should be tested. I hope this helps.

EDIT: Added K, not 265Ohm

[semanticart]

Thanks for your notes.

Sorry, I should have been clear: I got those readings in the diode test mode.

[Moralless]

Variation like that shouldn't really be something to worry about, if you're worried about the quality of your multimeter I suggest touching the two probes together while in the diode testing mode and if the value displayed comes out to be 0 (a little over would be ok but ideally it should be 0) then it should be working fine.

[hasu]

I think you can measure forward voltage in diode mode of multimeter in most cases.
Check manual of your DMM.

[RickyJ]

Don't bother with resistance measurements with diodes.  If the diode test shows 0.0V, it's shorted and then you can verify with resistance.  Basic Silicon diodes should read as ~0.6-0.7V forward, and oL (out of range) in reverse.  You won't typically see Germanium diodes in keyboards, but if you see them in the wild they'll show ~0.3-0.4V forward. 

[semanticart]

Thank you all for helping with my confidence here. My takeaway is that as long as they're not shorted, I'm good to continue.

(My multimeter does read 0 when I touch the probes together.)

[bpiphany]

Diodes doesn't behave like resistors. So in some sense they don't have a resistance. They have a voltage drop, like said above. Many multimeters should show this voltage drop if they can go high enough. I think my DMM in diode test mode use a constant current circuit and tries to run a 1mA current and then tell me the needed voltage.

My guess is that the value you get in resistance mode for a diode varies from meter to meter,  depending on what voltage/current reference the particular meter uses. A certain voltage drop over a resistor at some current would tell the resistance, fooling a DMM to output some resistance value even for resistors. This value would depend on the model of DMM and the method it uses to measure resistance.

Does anyone who knows more about DMMs want to confirm or fill in on how they work?