Frequently Asked Questions
When do I need to change the battery in my product?
Batteries should be changed when the battery voltage falls below 7.6 volts.
What is the effect on accuracy when the 9V battery voltage starts failing?
There is a negligible effect of decreased battery voltage, down to the minimum battery voltage of 7.6V. This is due to the use of linear voltage regulators on the DMMCheck Plus.
How do I change the battery?
Be mindful of static electricity, follow proper grounding protocol. The four screws on the top need to come out, the top board lifts out and the battery is underneath in a snap-in holder. Lift up gently on the battery (away from the holder) and it will pop out. Install in reverse order.
Is there any warm-up or stabilizing time?
Yes, please wait 10 minutes prior to use after turning on your DMMCheck Plus, unless you have a Rev 8 or higher with the external power supply and the unit is left on. For the highest accuracy, the ambient temperature should be as close as possible to the calibration temperature noted on the unit (typically 71 degrees F).
Is there any benefit to running your product continuously from an AC supply with battery backup?
Yes, the aging rate of the LT1021 voltage reference IC, used in the DMMCheck Plus, is proportional to the square root of the number of powered-on kilo-hours. For example, if, say, the voltage gradually drifts 10uV in 1000 hours, then the drift in the next 4000 hours would be expected to be 20uV. In other words it becomes more stable the longer it is on.
Do you ship to destinations outside of the USA?
Yes, we accept international orders. If you do not see your country on the list of ship-to countries, please contact us. International shipments may be subject to additional shipping costs to ensure safe and expedient delivery. FedEx shipping is available upon request. EU customers may also order through Welecton, detailed further in the "INTERNATIONAL CUSTOMERS" tab.
How much of a load can I connect to my DMMCheck Plus?
The LT1021BCN8-5 voltage reference IC, used in this product, has a worst-case load regulation value of 20ppm/mA. This means that for every 1mA of load current, the output can change by up to 100uV. Our testing indicates that this specification is conservative and most IC's are at least twice as good as this worst-case number. This load regulation specification is good to loads up to 10mA. We recommend a load of 1 MΩ or higher for best accuracy.