Hi,
I have an HP 5334A frequency counter and I want to install a 10MHz oven quartz oscillator to improve the accuracy. Although it’s not hard to find the oscillator, getting the support PCB is proving tricky. So I thought I would make one as it’s not a complex circuit or layout. Spacing of mounting holes etc is a bit more tricky - ?but I mocked up a prototype with cardboard to get rough sizing etc.

My question is about circuit grounds. The circuit (attached) has several separate supply grounds and my question is about the note 3 regarding “instrument common” and “digital circuit return”. They are distinguished on the schematic but appear to be connected on the PCB (see attached pic). For example C1 and C2 are clearly connected to edge connector pin 4 although they are different “grounds” according to the note.

could anybody advise me on what the best thing to do here is please? Are they the same?

thanks

Tonys

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开云体育

regarding grounds:

you're dealing with what's called circulating currents, or ground currents.

Let's say that you have an analog circuit, and that its ground is common (on the board) with a high power circuit.

as the high power circuit operates, the analog ground goes up and down, and could cause any number of problems with the analog circuit.

The trick is to make sure that the ground currents from the high power circuit don't flow through the analog ground, keeping the analog ground steady (and quiet).

A way to ensure this is to connect the analog ground (separate!) and high power ground (separate!) and digital ground( separate!) at only one point, which is where power enters the board.?

Look up the concept of "star grounding", for example.

the grounds are the same, in that they're all ground.? They are not the same in that they are NOT the same ground.

Hope that helps a bit, especially the lookup topic.

(NOTE: grounding is not a simple topic, and there are many different opinions).

Harvey