Hello could you give me a support regarding the probe please?
We have got a Lakeshore 425 gaussmeter, with HMMA-0604-TH display shows "larger offset than expected" with HMNT-4E04-VF works fine. Is the probe broken? Is there any solution how to fix it or is the probe damaged?
Post by Lake Shore Jeff M on Sept 1, 2021 6:37:00 GMT -5
The Offset Larger than Expected error you encounter when performing the zero gauss function normally indicates that the hall sensor has been damaged. This can occur if the tip of the probe comes n contact with the hard surface of the material you are measuring. It can also occur if the probe is dropped or is subjected to Electrostatic Discharge. Under most conditions, this is not repairable and a new probe is needed.
I suggest you inspect the tip of the probe under a Microscope or some other method of magnification and look for evidence of scrapping or chips in the epoxy paint that covers the tip. If you do not see and issues, use a digital Multimeter and measure the resistance between the following pins on the connector at the end of the cable:
Pin 1 to Pin 9 Pin 8 to Pin 15
In both cases, you should read a resistance of approximately 2.7 Ohms. Reading greater than 4 indicates severe damage and the probe is unrepairable.
If everything looks OK the probe would need to be returned to Lake Shore for further analysis. If that is the case, please contact our support team at [email protected] for additional help.
Dear Jeff thank you for the fast response the resistance values are 1-9=1.47 Ohms, and 8-15=2,08 Ohms. The tip looks realy bad uder the microscope, thera are some scratches and subsrate is viseble on some places.
The gaussmeter with this probe does not indicate last digit as in the past and has offset aproximately 10% neg. vs pos. orientation.
Post by Lake Shore Jeff M on Sept 3, 2021 9:48:12 GMT -5
If you are not seeing the offset larger than expected error, but so see the hall substrate exposed, it is just a matter of time before the probe fails completely. The difference in the readings can be explained by the position of the hall sensor in respect to the field as the sensor is on ne side of the stem so that slight distance difference can make a difference in the reading.
If you are still seeing the offset error, you will need to purchase a new probe.