Multimeter Ceramic Fuse Replacement

If you need replacing a fuse on your multimeter, you may find this reading useful. In this post I will share with you where you can buy cheap replacement ceramic fuses and how to make your DMM accept 5x20mm and 6x32mm fuses. I will also give some information regarding fuses and counterfeit fuses. In this case I am replacing the 1A fuse on a Uni-T UT61E multimeter, but this is applicable to most multimeters. You can read my review and teardown of the Uni-T UT61E multimeter here.

Ceramic vs. Glass fuses

The Uni-T UT61E, like many "better quality" DMM's, uses ceramic fuses. Ceramic fuses are better than the more common and cheaper glass fuses. They have a feature called High Rupture Capacity (HRC). Ceramic fuses have a ceramic tube, and all the empty space inside is filled with sand. If a very high current occurs, an extremely high amount of heat is created inside the fuse. That heat melts the sand filling of the fuse into glass. Since glass is an insulator, it suppresses any arc-over instantaneously. This behaviour minimizes the possibility of a dangerous high arc current, which is what happens if a normal glass fuse fails to break a heavy fault current. Unlike sand filled ceramic fuses, if a very high arc current goes through a common glass fuse, it can generate an explosion that shatters the fuse and lead to damages and serious injuries. 

Sources of 6x25mm ceramic fuses

The Uni-T UT61E uses two ceramic fuses, one 6x25mm 10A and one 6x25mm 1A. The original fuses are branded AsiaFuse BS1362. Unfortunately, it turns out that cheap BS1362 6x25mm ceramic fuses are hard to find. The more common BS1362 6x32mm fuse size is available from multiples sources though. And since the Uni-T UT61E PCB layout accepts 6x32mm fuses also, it's just a matter of moving one of the fuse holder terminals to a different position. Take a look a the following picture.

In the above picture, since a 6x25mm fuse was not available, I managed to use a 5x20mm glass fuse temporarily while my order of 6x25mm ceramic fuses did not arrive. It was a matter of carefully tightening the fuse support until it hold the smaller 5x20mm fuse securely in-place.

These are the BS1362 ceramic fuses I received from AliExpress. They are branded Bussmann and costed US $2.50 for a pack of 10. And here is the Uni-T 61E after the 1A fuse was replaced.

Unfortunately, after careful inspection and despite apparent good build quality, the fuses I received appear not to be genuine. However, since I determined they are safe to use (read below), I'm happy.

Buy BS1362 ceramic fuses from Banggood!

Counterfeit fuses 

Since branded ceramic fuses are much more expensive than glass fuses, there are counterfeits with varying levels of quality. In many cases it's very hard to tell if a ceramic fuse is genuine or not. One can visually inspect and compare the suspect fuse with an original fuse sourced from a reputable distributor. If you buy a set of ceramic fuses I recommend you open one to see if it is really filled with sand. Needless to say, counterfeit fuses can be dangerous!

BS1362 Fuse Specs Datasheet
Counterfeit Fuse Information
Review of Uni-T UT61E

BSide ADM04 Mini Multimeter Review & Teardown

The BSide ADM04 mini multimeter is a 3 1/2 digit small and inexpensive portable digital multimeter with some special features. One of the features is the non-contact voltage detection (NCV) function. This enables you to locate hidden live mains wires behind a wall. The ADM04 mini also has a Hold function and LCD backlite, something that even some more expensive multimeters don't have. But that's not all, it also has a spotlight! Yes, press a button and you can turn your multimeter into a flashlight. So, this is clearly a multimeter ideally suited to be carried around. Lets take a closer lock at the BSide ADM04 mini multimeter.

Features:
3 1/2 digital LCD display.
Mini pocket Auto range digital multimeter.
Measure DC/AC voltage, DC/AC current, resistance, and diode & continuity check.
Data Hold function.
With NCV (Non-contact AC voltage detector) function.
With backlight and work light.
With protection case.
Low battery indication.
Auto power off.
Safety rating: CE CATIII 600V.

Specifications:
DCV: 200mV/2V/20V/200V+-(0.5%+3), 600V+-(0.8%+5)
ACV: 2V/20V/200V+-(0.8%+3), 600V+-(1.0%+5)
DCA: 200µA/2000µA/20mA/200mA+-(1.8%+5)
ACA: 200µA/2000µA/20mA/200mA+-(2.0%+5)
Resistance: 200Ω/2kΩ/20kΩ/200kΩ/2MΩ+-(1%+3), 20MΩ+-(1.2%+15)

General characteristics:
Operating Temperature & Humidity: 0~40°C(32~104 °F), <80% RH
Storage Temperature & Humidity: -10~60°C(14~140 °F), <70% RH
Product Size: 130x62x27mm(5.4"x2.5"x1.10")
Product net weight: 150g/0.34lb
Colour: Black + Blue
Power Supply: 2 x 1.5V AAA Batteries (NOT included)

Appearance

The first thing that catches your attention is the small size of the BSide ADM04 multimeter. Although not the World's smallest multimeter, it will fit a large pocket. The multimeter case is protected by a silicone sleeve. The silicone sleeve protects the multimeter from falls and prevents the multimeter from skidding on the work bench. You will also notice that the test leads are not the usual detachable banana type cables, but are instead attached permanently to the multimeter. Since the ADM04 does not have some functions that would require the use of more than two multimeter inputs, for example high currents measuring, there is no need for detachable multimeter test leads. The test leads appear to be of good quality. The probes have detachable sleeves.

Non-contact voltage detection function

To use the non-contact voltage detection feature put the multimeter rotary switch in any position other than Off and point the bumpy part of the top of the multimeter to where the wires would be. If live AC wires are detected an LED near the top of the LCD will turn red. My tests show that the multimeter can detect live AC mains wires behind walls as long the wires are not to far away or the wall is not made of cement. Mains wires should be easily detected in plaster walls. Detection distance will vary, but it should work at a distance of up to about 10cm.

Voltage test
Both DC and AC measurements where within the accuracy specifications.

Current test
Current tests where within the accuracy specifications. Note that the ADM04 multimeter is capable of measuring only up to 200mA maximum current.

Diode test

Diode test range is 1V with 0.001V resolution and about 1mA test current. The display shows the approximate value of diode forward voltage drop. Open circuit voltage is about 1.6V which will be a problem when testing some LED's.

Continuity test

The built-in buzzer sounds when the measured resistance is less than about 50Ω. Response time is not fast, but it's OK.

Hold function

Reading values can be frozen on the LCD by pressing the hold button. The multimeter does not have auto-hold function.

Backlight and flashlight

LCD backlight is turned On by pressing the backlight button for 2 seconds. Backlight turns Off automatically after 15 seconds. The flashlight consists in a white LED with a lens and is activated simultaneously with the LCD backlight.

Test leads

The test leads are rated 600V CATIII/1KV CATII. They appear to be of reasonably good quality and made from silicone wire. The probes have detachable sleeves.

Battery replacement

The BSide ADM04 mini multimeter is powered by 2x AAA batteries. The battery compartment can be opened by removing a screw on the back.

Fuse replacement

The multimeter uses a single 250V 250mA ceramic fuse. To replace the fuse it is necessary to open the multimeter case.

Tear-down

The multimeter can be opened by removing the protective rubber case and unscrewing four screws. The battery compartment connects to the main board by two springs.

The multimeter uses a single board design. Component layout is good without any bodge wires in sight. Soldering is also good.

Input protection is accomplished by a single 250V 250mA ceramic fuse, two PTC's, diodes and resistors. Since this multimeter does not have a high current input, the usual wire current shunt and high current fuse are not present.

Verdict

The BSide ADM04 mini multimeter is a 3 1/2 digit portable digital multimeter with some welcomed added features and good build quality. The multimeter comes with a user manual in good English, something that more often than not is not the case. If you don't need to measure currents higher than 200mA, this is a good little multimeter to carry around. It is adequate for low voltage, low current circuits.

BUY THE BSIDE ADM04 MINI MULTIMETER FROM BANGGOOD

Need a better multimeter? Then take a look at my Uni-T UT61E multimeter review.

New to multimeters? Read my Multimeter buying guide.