Uln & udn protection

Hi all ,
I want to protect ULN2803 (NPN Array Transistors , Active Low) and UDN2981(PNP Array Transistors , Active High) , How could I do that ?
The board I'm designing is a tester so I don't know what is going to happen ,
Maybe just for a simple mistake in assembling the parts , ULN & UDN see unexpected voltages at their outputs . I can't use a series resistor cause it limits the current .

For ULN , I decided to use a relay to connect emitters to 2 resistors to verify the voltage between these 2 resistors and finally decide if the collector is ok or it's directly connected to +12v and then if the condition is ok I switch the emitter to GND .

For UDN , I decided to use a relay to connect emitter to 2 resistors to verify the voltage between these 2 resistors and finally decide if the collector is ok or it's directly connected to GND and then if the condition is ok I switch the emitter to +12v .

Is it correct ?
In other way :
Are Va & Vb different enough for ADC ?
Are Vc & Vd different enough for ADC ?

Thanks in advance

UP Please ?

I didn't understand the question, protect the drivers from what?
If you want to protect it for error in assembly then I can only think of a power supply with a limited current so that it can't damage the device (or pay attention while putting devices on the board ).

Alex

can you use an26 or other opto isolalors?