E3610A current meter mod

[sync]

Hi

One thing that annoyed me with my E3610A PSU was that the meter only has 10mA resolution. I want 1mA. I moded it to a dual range meter. A new 1000mA range (it only has 3 digits) and the old 3A one.

The meter uses a classic 7107 with 2V input range. Only up to 0.3V is used (3A with a 0.1 Ohm shunt). I modified the 7107 to 200mV input. This gave me the 1000mA range.  For the 3A one i use a 10:1 voltage divider. The switching between them is done by CMOS switches. A ATtiny44 is used for auto ranging. To do this it monitors the display segments. Over 999mA it switches to the 3A range. Under 0.9A it switches back to the 1000mA one. I added a 1s delay to prevent oscillating between the two ranges.



I added the red components. To change the 7107 to 200mV the existing R1 and C3 are changed to 33k Ohm and 470nF. The inserted 47k resistor between Vref and the R3 trimpot gives a finer adjustment for calibrating the 1000mA range.

The voltage divider and the CMOS switches are simply inserted at the input of the current meter. The trimpot is used for calibrating the 3A range. The ATtiny is directly connected to the LED display segments for monitoring them. It also drives the decimal points. DP1 for the 1000mA range and DP3 for the 3A one.

E3610A_current_meter.ino is the Arduino source code.

[Len]

The ATtiny is "watching" the display so it knows when to switch ranges? That's a clever hack. 

[sync]

The ATtiny is "watching" the display so it knows when to switch ranges? That's a clever hack. 

But an old one. In the ICL7107 datasheet is a similar circuit using logic gates.

[bdivi]

why not move the decimal point before the mA value - .234 instead of 234. ? I guess it will be better visualy

[sync]

There is no decimal point before available. I played with the idea to mount a LED for it. But then I took the easy way.

[elektronchika]

Cool, I like this idea