I do not blame the bystander, i blame the package. It is absurd that for a 170 dollar instrument ( and I have seen much higher prices, the IET is 350) you get it delivered with a powersupply that can kill your meter and influence the measurements like shown by two people in the other topic. I do not care about the cause of the roblem and that you can solve it yourself, the manufacturer sould olve that. You pay for the total. And as a total it stinks, that is what I have against it. Not about accuracy.
And the worst part is they knew, more people complained, they still shipped it untill enough complains came. Then the advise came not to use the shipped psu instead of replacing it by good ones. How hard is it to make or buy a decent psu and test it before shipping
It is fine you have a version that runs on 9V, but they all should do that. Uniform erformance, repeatabiltiy ect and some folks here have tried to operate it at 9 V and that did not work so it looks like there are more revisions of the instrument or the specs vary from product to product. Like the connection to the psu socket, wires to short, no problem, just solder it to a component with the tension of a guitar string ( see other topic)
So the thing as a whole package including service ect is what makes me dislike it, all this shows no respect for customers.
The accuracy is indeed "limmited" by the chipset but this is not the only thing. The final accuracy is depending on the right use of the chipset. Right distances, 4 wire technic ( in fact, the IET uses a 5 wire technik ( the guard wire, two sense and two source) , the used resistors, other parts and terminals ect.
Your GR1608 is beautifull, what year it is ? Mine was broken when I got it, i repaired and calibrated it with help from Henry Hall, the designer. A very nice and helpfull man. It is my favourite allround brigde ( i so have the handy GR1650B and a GR1620 that was used by GR self)
You know the GR is a 3 terminal device ? Because you now again used wires. Those wires and the terminals should add about 2 to 6 pF, the HP is also only accurate when used in 3 term mode. Many people start screwing in it to adjust it in 2 terminal mode but that does not work, it needs the guard to cancel the capacitance between standards and inner cabinet. Calibrating one is a hell of a job.
Release the clip between low and ground now you have three terminas. The third terminal on your GR is a more or less hidden one. There is a screw under the two DUT terminals, this is made to connect a fork terminalfonnected to the shielding of the low cable, or to both cables. The low is the most important. In that case you can use ( even longer) coaxial lines without getting the faults the two short wires introduce.
(but it is easy to measure, just measure the two wire at the same distance and position as an open. This is the value you have to subtract. Measuring a cap with a ESr of a few 10 mOhm in series with two long cables with a resistance of also a few 10 mOhm changes D. That is not strange, but I think you know that.