Week Two Blog

The A/B switch does not switch between voltage sources. It switches between which voltage source is to be measured on the meter. If the switch is on A, source A is shown on the meter. If the switch is on B, source B is shown on the meter. Even if the switch is turned to B, source A will still give an output.

The current specification for the power supply is either 0.5 A or 4 A, which means that the channels can give a maximum current of either 0.5 A or 4 A. The fixed channel has a maximum current of 4 A while A and B have a maximum current of 0.5 A.

The power supply has two main operation modes, tracking and independent. The independent operation mode keeps all three channels separate and three different voltage values can be put out at one time. The tracking operation mode allows the user to wire the A and B channels together, either in series or parallel. Wiring in series will double the voltage. Wiring in parallel will double the current. Below is a video of the different ways you can wire a power supply.

You can generate a 30 V output by wiring the two channels in series and setting the voltage to 15. When connecting the leads you connect the positive to positive and negative to negative.

To generate a -30 V output, the wiring remains the same except for the fact that the positive of the DMM is to connect to the negative of the power supply and the negative of the DMM is to connect to the positive of the power supply.

You can generate both a positive and equally negative voltage at the same time if you ground the positive of B, connect positive of DMM1 to negative B, connect positive B to negative DMM1 and negative DMM2, and lastly connecting positive A to positive DMM2. Basically, the entire power source is wired in series. 

When 5 V are applied to a 100 ohm resistor, both the power supply and the DMM read 50 mA. When adjusting the current knob, the LED lights on at just under the left horizontal. If straight downwards is set to be 0 degrees and the knob moves clockwise, the LED would light on at a little less than 90 degrees. If the value of current limit is decreased with the current knob, both the voltage and current decrease linearly.

The fuses for both the DMM and the power supply are located on the back of the mechanisms, under the power cables. Fuses are used on this equipment to ensure that the amount of current flowing through the machine is not too high to cause damage to the machine. A fuse will blow and stop the current from flowing if it becomes a dangerous amount.

When taking resistor measurements, there is a 2 wire option and a 4 wire option. The 2 wire function reads the resistance directly on an ohmmeter. The 4 wire function reads voltage with 2 wires and current with 2 wires, then uses ohm's law to calculate the resistance. 4 wire seems to be more accurate on a smaller resistance scale.

You should work safely when measuring a large amount of current, as it can be very dangerous. To measure current on a DMM you should break the loop to allow the current to flow through the DMM and back through the circuit.