Calibrating a 30 years old analog multimeter: Philips Multitester UTS001 ? - Page 1
Forum section: electronics / testgear

author: RK_aus_S
author_rank: Contributor
timestamp: September 29, 2018, 10:30:58 am
content: HiI wonder if it's possible tocalibrate my 30 year old Philips UTS001 multimeter:This device:https://www.radiomuseum.org/r/philips_multitester_uts_001.htmlThe schematic diagramm:https://www.rsp-italy.it/Electronics/Instruments/Philips/_contents/Philips%20UTS-001.pdfIs there anybody who can imagine which of the 3 potentiometers (R21, R22, R23) do have which calibration purpose? If there is somebody with good knowledge on old analog multimeters, it would be kind if he has some advices for me.

author: SeanB
author_rank: Super Contributor
timestamp: September 29, 2018, 12:27:49 pm
content: You start with the DC voltage ranges. Get a known voltage source, probably a 9V battery that you have new, and measure the voltage of the battery with another calibrated meter, and adjust R22, with the meter in the 10VDC range, to correspond with this voltage. Prior to that make sure the meter movement is correctly on zero, with the meter on it's back, and adjust the mechanical zero on the meter carefully to get it exactly on zero. Once you have your single point check on DC voltage, you do not adjust that pot again.Current ranges. Get a known current source, probably that 9V battery that you have, in series with this meter, a meter in calibration in DC current mode, and a series resistor of around 1k and check the displayed current is correct with the meter in the 3mA DC current setting. This is not adjustable, but is merely to check basic accuracy.Finally you need to do the AC voltage calibration. For this you need a small iron core mains transformer with a 9VAC secondary, and measure the AC voltage with the other reference meter, and adjust R21 with the meter in the 15VAC range to match.Resistance ranges check the meter will zero on all resistance ranges with the Zero pot R23, and then you can check with the 1k resistor you have that the x100 and x1k ranges read roughly the correct value of the resistor.Again remember the basic accuracy specs are 2% at best for DC voltage, 3% for DC current and around 5% for resistance, and AC voltage and current are only within 5% past half scale, they will under read below that.Reference meter can be almost any other digital multimeter with a 3 1/2 digit display, provided that it has some published specification for accuracy ( leaves out the cheaper DT830 and clones, and the cheap ones you get around) that is better than this meter specifications in the voltage and current ranges that you will be using. If it has autoranging it will most likely be usable for this check.

author: xrunner
author_rank: Super Contributor
timestamp: September 29, 2018, 12:46:20 pm
content: Quote from: RK_aus_S on September 29, 2018, 10:30:58 amI would say the 4.7k pot is for DC and the 47k pot is for AC. The 150k is probably for a Zero set adjustment. Someone will come along and either back me up or refute me.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 29, 2018, 03:05:30 pm
content: Take the trim pots values before fiddling with them and turn them slightly to see what ranges change in values ??