Multimeter use EX3 OL display on multimeter meaning and measuring Example

OL display on multimeter meaning and measuring

What does OL mean on a multimeter , this is the frequency ask question from digital multimeter user. It has many meaning , it depends on what is the test function range that you set. I have researched from many multimeter manual and found that OL = Over a range Limit and other detail at measuring explaination when LCD display " OL" mean Over Range and it suggest user to change the range to higher range or seek the appropriate range for the measured amount. For example when you measure 9VDC battery and use 0.000V range by manual selection , the testing result display OL as photo , it mean this range selected is not suitable for 9VDC and you have to change setting to higher range. OL display also displays with other test function range such as resistor measurement , current measurement , capacitor test , temperature measurement etc. View photo below for more understanding.

OL display , measuring example for range selection is not suitable.

0.000 DC voltage range set by manual range selection for 9VDC battery

Test multimeter OL display on multimeter

It display OL because this 0.000 DC voltage range is not suitable for 9VDC.

The solution is setting to auto range or use higher range. (For OL display example only)

00.00V range set by manual range selection for 9VDC battery

It displays 9.43V as it should be (mean 00.00 DC voltage range is suitable for 9VDC )

The good measurement , you have to select the right range and right test function before operating any measuring. Unknown value it suggest to chose the highest range first. For advance multimeter it has auto range , but , for low cost multimeter has only manual range selection and user need to study how to set the suitable range for the target measurement.

OL display when testing condition of components = not shorted , not connected.

The other meaning of OL display on test function such as diode test , continuity check . It indicates the condition of component "good" or " bad" , defective. OL display for diode check , In case of reverse bias it means diode is not shorted , 2 terminal is not connected and when supply reverse bias to diode it has to display "OL" as it should be = good diode. Example will be shown by photo.

Forward bias to a diode , it displays 0.3-08V = good diode.

Reverse bias to a diode , it displays OL = good diode and this time OL mean "not shorted "

OL display when we use continuity check. When checking switch at OFF position it has to be not connected , not shorted condition. This time OL display mean contact is not shored (good contact). Technical term NO terminal ( Normally open) it mean contact is not connected and the testing result get " not connected " as it should be. When changing the switch position to "ON" it means internal contact is connected or shored , the display should be 0 ohm for good contact. If the display still show OL it means internal contact is not connected as it should be condition , so OL = bad contact.

OFF position , internal contact of switch is not connected , OL display means contact is not connected. So switch contact is good as it should be.

Test multimeter 0L display on multimeter

ON position , internal contact is connected , the display has to show 0 ohm ( shorted) for a good switch If display show OL it means not connected contact , this case it is a bad contact ( switch)

ON position , the internal contact is connected , but , multimeter display OL means internal contact is not connected as it should be so this case it is a bad switch contact.

Read more topics of testing , from here.

How to check electronic device

Multimeter use EX4 test AA battery and 9V battery with multimeter

Multimeter use test battery

Analog multimeter has 1.5V BATT range and 9V BATT range for especially testing small battery. BATT range operation is different from DC voltage range. BATT range has accurate measurement and precise method to test AA and 9V battery. BATT range has internal low value resistor and when set to this range the current from test battery will flow through the resistor and there is some voltage across the resistor , the multimeter will display voltage from the resistor. But , DC voltage range is tested while test battery is open circuit (current does not flow) because DC voltage range has high input impedance so it is not a precise measurement to test AA and 9V battery , however , In many case it is still useful to test battery with DC voltage range (Rough or approximate measurement).

Step to check 1.5V 9V battery with multimeter.

1. Insert the red test lead to + terminal and the black test lead to COM terminal.

2. Turn range switch to 1.5V BATT for testing 1.5V AA battery and 9V BATT for testing 9V battery.

Test AA 1.5V battery with 1.5V BATT range

Test 9VDC battery with 9V BATT range

Battery test range ( BATT)

3. Reading the test result.

Good battery : the pointer will point at Good scale area.

Good or bad ? : the pointer will pint at Scale ? area , this condition battery can be used for low current consumption device , such as wall clock , but not suitable for device need power.

Bad : the pointer will point at Bad scale area , it's time to change a battery.

Some analog multimeter and digital multimeter has not BATT range , this case it will use DC voltage range to check battery but is not a precise measurement to test battery. DC voltage range to test battery is approximate measurement which is still useful and acceptable for many case.

Test NPN PNP transistor with a digital multimeter and identify transistor pinout

Test NPN PNP transistor with a digital multimeter

Test condition of electronic component start with test resistor , capacitor , diode , LED , and the next component is transistor. Before testing transistor you have to study how to test diode firstly because it the same process just more detail. The parity of test leads and diode , forward bias , reverse bias also use to describe how to test transistor. Diode model is used to explain how to test transistor. NPN type 2 diode is common anode connection and PNP type 2 diode is common kathode connection.

NPN Transistor and 2 diode model to test NPN type.

PNP Transistor and 2 diode model to test PNP type.

Step to test transistor with a digital multimeter .

1. Turn the range switch to diode test.

2. Connect the test lead with B and C terminal and read the measured value. Then switch the test leads and read the measured value again . Good transistor will display 0.5-0.7V 1 time and "OL" 1 time. Shorted transistor will display 000V 2 time and open transistor will display "OL" 2 time.

The terminal arrangement of example transistor for test demonstration. Different transistor part number may has different terminal designation.

B and C terminal test , good transistor will display 0.5-0.7V 1 time.

B and C terminal test , good transistor will display "OL" 1 time. ( switch the test leads )

3. Connect the test lead with B and E terminal and read the measured value. Then switch the test leads and read the measured value again. Good transistor will display 0.5-0.7V 1 time and OL 1 time. Shorted transistor will display 000V 2 time and open transistor will display OL 2 time.

B and E terminal test , good transistor will display 0.5-0.7V 1 time.

B and E terminal test , good transistor will display OL 1 time. ( switch the test leads )

4. C and E terminal test , connect the test lead with C and E terminal and read the measured value. Then switch the test leads and read the measured value again. Good transistor will display OL 2 time and shorted transistor will display 000V 2 time.

5. All step of testing must be all good condition so the transistor is still good ( step 2 , 3 and 4 : B-C terminal test , B-E terminal ,C-E terminal test). If there is only any of 1 step fail , that transistor is bad.

C and E terminal test , good transistor will display OL 2 time

C and E terminal test , good transistor will display OL 2 time ( switch the test lead )

Identify transistor pinout.

1. Find B terminal , from 2 diode model at the beginning , random the test around 6 times and you will find 2 time that the meter display 0.4-0.7V , the B terminal is connect with any test lead (not move) and make the other test lead that move to terminal no.2 and no.3 and meter display 0.4-0.7V 2 time ( B-C , B-E). From 2 photo below so the red test lead is B terminal.

2. Find C and E terminal , V BE > V BC , V BE is more than V BC so terminal No.3 is E terminal and terminal No.2 is C terminal.

Hold the red test lead with terminal no. 1

--------------------------------------------------------------

Choose these articles to read more , from here .

Test IGBT Part 1

https://www.testmultimeter.com/2021/11/multimeter-use-how-to-test-igbt.html

Test IGBT Part 2

https://www.testmultimeter.com/2020/12/test-igbt-with-multimeter-bad-or-good.html

Test SCR Module

https://www.testmultimeter.com/2020/12/test-scr-thyristor-module-with.html

Test IGBT Module

https://www.testmultimeter.com/2020/12/how-to-to-test-igbt-module-with.html

1) 30 testing of electronic devices

2) Test Triac with multimeter

3) Test SCR with multimeter

4) Test MOSFET with multimeter

------------------------------------------------------------

Test a Diode with Analog Multimeter check foward voltage drop forward current and reverse current.

Test a Diode with Analog Multimeter

We use LV and LI scale to test a diode condition. How to set those scale , it use Ohm range then reading the measured value from LV scale to test forward voltage drop (Vf) and use LI scale to test forward current and reverse current. This method can test LED and zener diode too. See photo below , LV scale range 0 - 3 full scale and LI scale range 0-15 full scale.

LI scale reading 0-15 full scale.

x1 Full Scale 150mA , multiplied by 10 with 0-15 reading

x10 Full Scale 15mA , multiplied by 1 with 0-15 reading

x100 Full Scale 1.5mA , devided by 10 with 0-15 reading

x1K Full Scale 150uA , multiplied by 10 with 0-15 reading

LV scale range 0 - 3 and LI scale range 0-15

Step to test Diode with analog multimeter .

1. Set the multimeter to Ohm range. Select the right range and turn rotary switch to suitable range. Multimeter will supply voltage and current to diode from the test leads. The voltage and current supply from internal AA battery which installed inside the multimeter.

Rx1 ( 150mA 3VDC ) for big diode.

Rx10 (15mA 3VDC ) for medium diode.

Rx100 (1.5mA 3VDC ) for small diode

Rx1K ( 150uA 3VDC) for test leaked current.

2. Plug the red test lead to + terminal and black test lead to COM terminal.

3. Zero Ohm adjustment before testing so it will get accurate measured value. Short 2 test leads together and adjust 0 Ω ADJ knob till the pointer point at 0 Ohm mean it is ready to test.

Zero Ohm adjustment

4. Forward bias to diode by connect the black test lead Anode terminal and the red test lead to Kathode terminal as photo. The black test lead will supply positive voltage and the red test lead will supply negative voltage ( it come from internal AA battery polarity ) so the diode will get forward bias.

Forward bias to diode

5. Read the measured value , forward bias case.

LV scale ( 0-3) as above photo diode has forward voltage drop = 0.7V

LI scale (0-15) as above photo diode has forward current = 12.5mA

6. Reverse bias to diode by connect the black test lead Kathode terminal and the red test lead to Anode terminal as photo below.

Reverse bias connection to diode

7. Read the measured value , reverse bias case.

LI scale (0-15) as above photo diode has reverse current = 0 mA

As reverse current of small and medium diode is very small amount micro amp ( such as 5.0uA) so the multimeter can not sense that micro amp current by setting X 10 range.

8. Check diode condition and summarize.

Good diode will get forward voltage drop 0.3-08V when forward bias testing.

Good diode will get 0mA ( very small amount uA) when reverse bias testing.

Bad diode ( shorted ) will get 0 Ohm and switch the test leads still get 0 Ohm.

Bad diode ( Open ) will get ∞ Ohm and switch the test leads still get ∞ Ohm.

Bad diode ( shorted ) , the pointer will point at 0 Ohm and switch the test lead , it still get 0 Ohm.

Bad diode ( open ) , the pointer will point at ∞ Ohm and switch the test lead , it still get ∞ Ohm.

Read more topics of testing , from here.

30 testing of electronic devices

How to check a capacitor with a Multimer Analog and Digital Multimer Measurement

How to check a capacitor with a Multimer

Capacitor is a basic components that use a lot on PCB. Film capacitor and ceramic capacitor has not polarity , but tantalum capacitor and electrolytic capacitor has polarity. Always discharge big capacitor and high voltage capacitor before testing and test it when there is not voltage present at the circuit. Unplug and remove power from circuit before measuring. Failure to provide those condition before testing it is a high risk of electric shock and the multimeter will damage too.

Step to check a capacitor with Digital Multimer.

1. Must remove power , switch off and discharge big capacitor , high voltage capacitor before testing. Test capacitor is performed when it is not on PCB ( not connected on circuit).

2. Turn the switch range to capacitor test function.

3. Connect the multimeter test leads with capacitor terminals.

4. Read the measured value.

Good capacitor will get measured value closet to it's value that print on label.

Shorted capacitor will display OL.

Open capacitor will display nF value which is capacitance of test leads only.

Degrade capacitor , measured value is too low and amount is different from original value.

100uF capacitor , get measured value as 98.9uF which is close to printed value ( good capacitor)

Multimeter display for internal open capacitor ( For demonstration purpose only )

Multimeter display for internal shorted capacitor ( For demonstration purpose only )

Film capacitor 5uF , get measured value as 5.16uF which is close to printed value.

Step to check a capacitor with Analog Multimer.

1. Must remove power , switch off and discharge big capacitor , high voltage capacitor before testing. Test capacitor is performed when it is not on PCB ( not connect on circuit).

2. Turn rotary range switch to appropriate range as list below.

X10K for capacitor value : less then 10uF

X1K for capacitor value : 10uF - 47uF

X100 for capacitor value : 47uF - 470uF

X10 for capacitor value : 470uF - 4700uF

X1 for capacitor value : 4700uF and more value

The good capacitor , the needle will move forward then backward at the end of scale. Electrolytic capacitor has very little leaked current so the needle will not fully move backward for some capacitor.

The needle will move forward then backward at ∞ for a good capacitor.

Leaked capacitor is a bad capacitor , the needle does not move fully backward at ∞ but it point at some high resistance. Switch the test leads and re-test , it will get the same testing result.

Open capacitor is a bad capacitor , the needle will not present any movement , it always point at ∞ scale . Switch the test leads and re-test , it will get the same testing result.

Shorted capacitor is a bad capacitor , the needle move forward and always point at 0 ohm scale . Switch the test leads and re-test , it will get the same testing result. ( this photo for demonstration only )