Cheap eBay PWM ... not working?

[HHP]

I recently purchased this PWM for use in a stir plate: http://www.ebay.com/itm/130574312785

I believe I have it wired correctly, there are only four terminals Input +/- and output +/-. One set is labeled +/- and the other m+/m-. I assume the +/- is the input and the other set is the output. I am running it with a 12v 1.5a power supply.

When I turn it on, the LED on the board comes on. If I have my multimeter on the +/- and I turn the pot, the voltage goes from zero up through 12 and then at the end back down to 0, and it is constant ... not pulsing. Also if I put the red lead on the m+ and black on m- the voltage actually reads negative (-).

Do I have the input/output backwards? should I try switching them? Is it just faulty?

 

[crane]

I can't comment on how to hook up the pwm, but I can say that most multimeters average the voltage over a certain time period and that most pwm circuits operate at fairly high frequencies. Therefore it is expected that your multimeter will filter out the high frequency pulsing and give you a DC average. So if the duty cycle of the pwm is 0% your meter will read 0V. If it is at 50% then you will see 6V. And finally if it's at 100% you will see 12V. If you really want to see the pulsing you need to hook it up to an oscilloscope.