Electrical probes to USB

[slayer38115]

Hello,

I need a set of Fluke probes to USB input. Mobile Solutions has the USBP3 kit for $229, Educar has the same kit for $99 but I've been trying to get a response from Educar for over 2 weeks with no answer. Anyone know of any other kits like these for around the $100 range? Or have plans, pinouts, etc. to build one. Model and part numbers would be great. I want to use REW to take electrical measurements in cars not just acoustic. The kits are probe to XLR, -20db attenuator, USB to XLR sound card cable, and a RCA to XLR adapter. mobilesolutions-usa.com/product-page/usbp3-test-cable-kit

Thanks,

 

[trobbins]

I'd caution what you may achieve with these, and you haven't identified the soundcard you want to use.

Most soundcards, and also REW, are for AC measurements, with a typical lower frequency response not extending below about 2-10Hz (due to soundcard roll-off). So not for DC measurement, or for scope type acquisition of one-off transients. It sounds like the probe kit includes a 10:1 divider option, but that has to be calculated in with a soundcard's input voltage clip/damage limit, in order to identify what AC signals/transients can be safely connected to. The 10:1 option also has to have an impedance compatibility with the soundcard input impedance.

 

[slayer38115]

I won't be measuring DC with REW, the purpose is to check frequency response of head unit output in vehicles. Also, for example, the mobile solutions kit includes a xlr to isb soundcard cable and -20db attenuator which allows direct input to a computer USB port.

 

[sam_adams]

USB to XLR soundcard cable.

Fluke TP88 Rigid Back Probe Pins.

Fluke TL175 TwistGuard Test Leads.

XLR Male to RCA Female Adapter.

In-Line XLR Attenuator Pad -10dB.

In-Line XLR Attenuator Pad -20dB.

Female XLR connectors at Parts Express.

That's essentially the Mobile Solutions kit with an extra attenuator thrown in. Your time and skill to make the test leads is required.

 

[trobbins]

Ta - I can now see that a simple ADC soundcard is embedded in the USB cable interface. The frequency response is not identified but probably 20Hz to 24kHz, and REW may be able to extend that down to under 10Hz with calibration. There is no clarification of input voltage capability, so some care is still needed with probing amplifier outputs, and a custom adaptor likely needed if outputs are class D or bridge mode. The attenuators are designed for 600 ohm termination, but the ADC input is not identified. It's nice that the probes have a CAT rating, but applying even 10% of any such rating with likely damage the ADC or attenuators. It seems a lot to pay for so sparse a specification.

 

[slayer38115]

That's essentially the Mobile Solutions kit with an extra attenuator thrown in. Your time and skill to make the test leads is required.

Thanks,

Ta - I can now see that a simple ADC soundcard is embedded in the USB cable interface. The frequency response is not identified but probably 20Hz to 24kHz, and REW may be able to extend that down to under 10Hz with calibration. There is no clarification of input voltage capability, so some care is still needed with probing amplifier outputs, and a custom adaptor likely needed if outputs are class D or bridge mode. The attenuators are designed for 600 ohm termination, but the ADC input is not identified. It's nice that the probes have a CAT rating, but applying even 10% of any such rating with likely damage the ADC or attenuators. It seems a lot to pay for so sparse a specification.

It is alot to pay which is why I'm looking at alternatives. Using the list in the previous reply, the kit can be built for about$100, thanks to that poster for the list..

The lack of in depth specs doesn't bother me too much in this case as Mobile Solutions is THE authority when it comes to mobile electronics installations. This type or I should say identical kit, is also used and taught by Educar for mobile electronics testing with a laptop.

I certainly don't need to see below 20hz since I typically set infrasonic filters at 25hz or 1/2 octave below tuning frequency for ported boxes and keep REW scaling from 20-20,000.

Again, the purpose of this kit is for headunit electrical measurement to test for things such as bass roll off and factory crossovers or filters. Anything on the output side of an amplifier I only use a scope for clipping and gsin set and then REW for acoustic measurement. The -20db Attenuator should protect the laptop from any high signal coming from the head unit.

 

[trobbins]

The -20db Attenuator should protect the laptop from any high signal coming from the head unit.

Just need to be aware if any clipping starts as volume is increased. The USB interface has an indicator, but no clarification if that is just for power indication compared to a signal level overload LED type indication - many common USB powered portable interfaces allow a higher signal level input, and some have LED level indication, but some don't, and so would rely on REW to be set to show high/overloaded signal level. Overvoltage transients are likely your main risk with permanent damage of the ADC.

 

[slayer38115]

Ok thanks for the tip. I'll see if any of these soundcard cables have an indicator that's more than just power.

Thanks