Device Connection Options

The version of the unit supplied is not fitted with an IEEE-488 connector (this is optional) but has a LAN connector for test environments using the newer LXI (LAN Extensions for Instrumentation) network based on Ethernet. The rear mounted USB port allows the unit to be connected to a computer where it can communicate using a virtual COM port or via USB TMC (Test and Measurement Class). Using a virtual COM port allows you to communicate via a standard terminal emulation program using the SCPI commands after the corresponding Windows drivers have been installed. Alternatively you can use the free Windows application HMExplorer which has a built-in terminal emulator function and also allows you to save screenshots, define an arbitrary waveform and store measurements.

The rear panel connector also allows the connection of an analogue control input voltage. This allows an external analogue voltage in the range from 0 to 10 V (or current from 4 to 20 mA) to control any or all of the three output channels. Assume, for example that channel 1 and 2 have been selected to be controlled by the analogue input. Using the menu the output voltage of channel 1 is set to 30 V and channel 2 to 20 V. Now as the analogue control voltage is increased from zero to 10 V the outputs from channel 1 and 2 will increase proportionally from zero to their maximum setup values.

Useful for development environments using multiple supplies, the sequence option allows turn-on of a channel to be delayed from 10 ms to 10 s after the master On/Off is activated. The analogue control input can also serve as an external trigger input which initiates pre-programmed processes in the power supply. A manual trigger pushbutton is also included on the front panel.

The EasyArb feature on the HMC8043 is Rohde & Schwarz’s very close approximation of an arbitrary waveform generator (AWG) function. Whereas AWG is usually time-based, in the MHC8043 it can also be event-based, which is exceptional in its price class. EasyArb allows the output voltage level on any channel to be defined with a resolution of 10 ms, 1 mV and 1 mA. The waveform can be defined using a maximum of 512 points and can be repeated a programmed number of times or indefinitely. Entering the data by hand using the front panel buttons can be tedious; HMExplorer is the more convenient option here.

Remote Voltage Sensing

The three channel version I tested has a rear socket which amongst other signals, offers remote voltage sensing for all three outputs. This is useful to remove the voltage drop produced in the cables supplying power to the load. This feature can also be handy when the supply is used to recharge a multi-cell rechargeable battery pack. It’s always a good idea to include an external diode in series with the battery pack when charging from a power supply. Without the diode, a power outage will often cause the energy stored in the multicell battery pack to ‘bite back’ and destroy the power supply output stage. The remote sense allows the battery pack voltage to be monitored directly, ignoring the non-linear voltage drop induced by the diode (Figure 5); the remote sense can compensate for a drop of up to 1 V max.