I have to control 4 proportional valves (Bürkert 2873 x 3 & 2875 x 1) installed on a gas line. These valves control signal type is 4-20 mA. I have a NI USB-X 6343 daq with 4 AOs of -10 - 10 V. How can I control these valves with this daq device? I am not familiar to electrics/electronics, that's why I am asking. Thanks in advance.