More toys!

The GW Instek multimeters that I purchased through an online auction finally arrived.  They work perfectly, with no funky voltage readings or anything alarming like the Fluke 8000A meters showed.


 I love these new meters.  Below, I'm testing the DC voltage function using the capacitor tester to provide DC voltage - lots of it!

Yeeehaw!  Ready to defibrillate!

Speaking of supplying DC voltage, I bought a very nice low voltage DC power supply - also manufactured by GW Instek, like the meter above.

It's a really sweet (and heavy) linear power supply, Model GW-3030DQ.  This is a regulated power supply, so there is a feedback circuit to maintain constant output voltage (or constant output current) as a circuit loads and unloads.  With this design, however, you can get into a runaway situation should a short circuit fault occur.

Under short circuit conditions, resistance in the circuit drops off.  This causes voltage to fall, so a regulated power supply will increase the voltage back to the setpoint.  The added voltage causes more current to flow through the circuit.  The extra current causes heating, which leads to thermal damage.  At some point either the circuit or the power supply experiences a failure due to current-induced heating. 

For the above reason, a regulated power supply usually has a current limiting device.  This one has adjustable current limiters, so that you can limit current flow into the particular circuit you need to provide power for.

A DC linear power supply creates more power than is required by the circuit, and the unused power is dissipated by resistors inside the cabinet.  When the power is needed, it is smoothly diverted out of the resistors and over to the circuit being powered, with very little voltage ripple.  The heat created by the resistors is removed from the case by a whooshing little fan.  It sounds a lot like a PC when you turn it on.  


Below, the new power supply.  Along the bottom, the two left (triple post) outputs are adjustable, both in current and voltage.  They can also be ganged together to provide either additional voltage or additional current.  The green digits are the voltage setpoints for each channel, and the red digits are the current limits for each channel.

The bottom right output is fixed at 5 volts with a 3 amp max limit.

I'm looking forward to playing with all this new stuff when the snow starts falling, and there's less other stuff - like landscaping, deck maintenance, and cutting fire breaks - on my plate!