Different reading in pH meter

Quality Control
1

I have 2 pH meter and both give 2 different readings ,a difference about 0.3. I check the electrode and its performance is OK. Can you tell me what can I check else.

Thanks

2

calibrate both ph meters with buffer solutions and then perform pH again.

3

I calibrate the ph meters with the same buffer solutions , the readings were 1.30 for Hanna and 1.66 for Consort

4

Try by exchanging the electrodes and see the difference to locate where the actual trouble is whether it is with the electrodes or with the basic electronic unit.

5

Are both equipment the same?
Are the electrodes for the same function?

6

If I am correct pH value may be change due to change in temperature, you have to verify that ATC is on in either pH meter and check MV value for both pH meter.

7

Please calibrate both pH meters with SAME standard buffer solution and adjust the pH reading of both (Hanna and Consort models) the pH meters to same value (1.30), if necessary. There is a knob provided to each pH meter to adjust the pH value to the desired standard buffer solution when pH is checked for standard buffer solution.
When bot the values are exactly matching only then determine pH of unknown sample solution on both the pH meters and compare. Ideally you should gert same pH readings.