What are some of the most common problems with LED display?
Author:Wu Qin Time:2021-06-11 13:35 Browse(398)
to judge problems, we must deal with them in a primary and secondary way, the obvious and serious ones first, and the small ones later.
In order to judge the problems, we must deal with them in a primary and secondary way, the obvious and serious ones first, and the small ones laterShort circuit should be the highest priority1. Resistance detection method.

What are some of the most common problems with LED display?

set the multimeter to the resistance level to detect the resistance to ground at a certain point of a normal circuit board, and then detect the same point of another same circuit board to test whether the resistance value is different from the normal resistance value. If it is different, the scope of the problem will be determined.
in this paper, the resistance detection method is proposed2. Voltage detection method.
adjust the multimeter to the voltage level to detect the voltage to ground at a certain point of the suspected circuit, and compare whether it is similar to the normal value, otherwise the scope of the problem will be determined.
the voltage detection method is used to detect the voltage to ground at a certain point of the suspected circuit3. Short circuit detection method.
adjust the multimeter to the short circuit detection gear (some are diode voltage drop gear or resistance gear, generally with alarm function) to detect whether there is a short circuit phenomenon. If a short circuit is found, priority should be given to solve it, so that it does not burn other devices.
this method must be operated under the condition of power failure.
to avoid damaging the meter.
this paper introduces the short circuit detection method4. Voltage drop detection method.
adjust the multimeter to the diode voltage drop detection level, because all ICs are composed of many basic single components, only miniaturized, so when there is current passing through a pin, there will be voltage drop on the pin.
generally, the voltage drop of the same type of IC on the same pin is similar.
according to the voltage drop value on the pin, compare the good and bad, This method has some limitations.
for example, if the device to be detected is high resistance, it can not be detected.
in this paper, a new method is proposedUnit board fault:A. The whole board doesn't light up1. Check whether the power supply is connected to the signal line.
check whether the power supply is connected to the signal line2. Check whether the test card identifies the interface.
if the red light of the test card flashes, it is not identified,Check whether the lamp board has the same power supply and ground with the test card, or there is a signal short circuit between the lamp board interface and the ground, which leads to the unrecognized interface.
(intelligent test card)3. Detect whether there is false soldering or short circuit in 74hc245.
check whether the corresponding enable (EN) signal input and output pins of 74hc245 are false soldering or short circuited to other circuits.
check whether there is false soldering or short circuit in 74hc245Note: check the power supply and enable (EN) signalB. In the oblique scanning.
regular interlacing is not bright, and the screen overlaps1. Check whether there is broken wire, virtual soldering or short circuit between a, B, C and D signal input port and 245.
check whether there is a short circuit between a, B, C and D signal input port and 2452. Detect whether there is open circuit, virtual soldering or short circuit between a, B, C and D output terminals corresponding to 245 and 1383. Detect whether there is a short circuit between a, B, C and D signals or a short circuit between a signal and groundNote: main signalC. When all lights are on, one or more lines are not on1. Detect whether the line between 138 and 4953 is open circuit, faulty soldering or short circuit.
the circuit is closedD. In line scanning.
two or more lines (usually multiples of 2, regular) light up at the same time1. Detect whether there is a short circuit between signals a, B, C and D.
the system can detect the short circuit between signals a, B, C and D2. Check whether the output terminal of 4953 is short circuited to other outputs.
check whether the output terminal of 4953 is short circuited to other outputsE. When all lights are on, there are single or multiple points (irregular) that are not on1. Find out whether the control pin corresponding to the module is short circuited to the line.
check whether the control pin is short circuited to the line2. Replace the module or single lamp.
replace the module or single lampF. When all lights are on, one or more columns are not on1. Find the pin controlling the column on the module.
test whether it is connected with the output of the driver IC (74HC595 / TB62726,,,)G. There are single point or single column highlights.
theOr highlight the whole line, and it's not controlled1. Check whether the column is short circuited to the power supply ground2. Detect whether the line is short circuited to the positive side of the power supply3. Replace the driver IC.
the driver IC is replacedH. The display is confused.
but the output signal to the next board is normal1. Check whether the latch output terminal of STB corresponding to 245 is connected with the latch terminal of driver IC or the signal is short circuited to other lines.
check whether the output terminal of STB corresponding to 245 is connected with the latch terminal of driver IC or the signal is short circuited to other lines1. The display is confused.
the output is abnormal1. Detect whether the clock CLK latch STB signal is short circuited2. Detect whether the clock CLK of 245 has input and output3. Detect whether the clock signal is short circuited to other lines.
the system can detect whether the clock signal is short circuited to other linesNote: it is mainly used to detect clock and latch signal.
it is used to detect clock and latch signalJ. The display is achromatic1. Detect whether the data terminal of 245 has input and output2. Detect whether the data signal of this color is short circuited to other lines.
the system can detect whether the data signal of this color is short circuited to other lines3. Detect whether there is open circuit, short circuit or false soldering in the cascade data ports between the driving ICs of the colorNote: the voltage detection method can be used to find out the problem easily.
detect whether the voltage of the data port is different from that of the normal one, and determine the fault area.
the voltage of the data port is different from that of the normal oneK. There is something wrong with the output1. Check whether the circuit from the output interface to the signal output IC is connected or short circuited2. Check whether the clock latch signal of the output port is normal.
check whether the clock latch signal of the output port is normal3. Detect whether the cascade output data port between the last driver IC is connected to the data port of the output interface or short circuited4. Whether the output signals are short circuited to each other or short circuited to the ground5. Check whether the output cable is in good condition.
check whether the output cable is in good condition50. The unit board is not bright, long bright, dark bright at eight or 16 points1. Visually check the module pins and leads corresponding to the fault for short circuit, false soldering and open circuit2. Whether the common connecting line between the upper and lower modules and the left and right modules of each cell (the unit board is divided into two cells) is normal (connect the multimeter to the ring terminal.
the lead wires of the line input terminal and each control input terminal of the measurement module). If it is, it is judged that the module is bad. If not, it can be eliminated by directly connecting it with thin wires instead of connecting it.
the system is simple and reliable3. A multimeter can be used to directly measure whether a single module is normal or not.
if so, it is judged to be an internal short circuit between the circuit board and the module. If not, it is judged that the module is broken, and it is replaced by the module of the same model.
if so, it is judged to be an internal short circuit between the circuit board and the moduleM. Several lines or the whole cell (the cell board is divided into upper and lower cells) are not bright, long bright and dark bright1. Visually check the corresponding tubes, through inductors and integrated circuits for false soldering, short circuit and open circuit.
if so, disconnect the short circuit and rewire the false soldering and open circuit2. Use a multimeter to measure whether the output voltage of each line tube is normal (multimeter measurement method: connect the black probe with GND and red probe to measure the voltage of each pin); If it is,
it is judged that the line output is open circuit with the corresponding module pin; If not, measure whether the input end of the tube is normal; If so, the line pipe is broken and replaced with the same type of line pipe; If not, measure whether the corresponding hc138 output is normal; If so, it is judged that the output end of hc138 is open circuit with the input end of the line tube; If not, hc138 is judged to be bad.
if not, hc138 is judged to be bad3. Replace the hc138 with a good 16p cable.
measure the voltage of hc138 address input 1, 2, 3 pins, gate 4, 5 (low level valid), 6 (high level valid) and whether the IC power supply is normal. If so, it is judged that hc138 is bad, and then (2) continue to check.
(4) whether the 5V connecting line between the two cells is disconnected.
if so, it is judged that hc138 is badIf it is, it can be connected directly with the same power line (generally, the whole cell is not bright or dark light).
if it is, it can be connected directly with the same power line4. Measure whether the line signals at the input end of the unit board (golden finger 26p can be regarded as 13 groups.
among them, 8, 9, 10 and 11 are line signals of l0, L1, L2 and L3 respectively) have internal short circuit, open circuit and whether the drive is normal after hc244 input. If so, measure whether the signal of hc138 input through hc244 drive is normal, and then continue to check with (2). If not, it is judged that hc244 is bad, Replace it with the same type of integrated circuit.
1N. There are no red or green cells in the unit board (the unit board is divided into upper and lower cells).
there are no red or green cells in the unit board1. Visually check if the integrated circuit, 26p cable and 5V power supply are normal (the good 26p cable can be directly used for replacement).
check if the integrated circuit, 26p cable and 5V power supply are normal2. The 26p connecting line between the unit boards (1 and 2 pins of 26p cable are red signals.
3 and 4 pins are green signals) and the output of the front unit board (judgment method: take a long 26p cable to discuss whether the cross interchange connection is normal, then it is judged that there is a problem in the back; If yes, measure the red signal input to hc244, and then check whether the 14 pins sent to hc595 after driving are normal (if yes, and other pins of hc595 are normal, judge whether hc595 is bad, and replace it with the same type of integrated circuit). If no, check whether 26p cable has problems and input is abnormal.
if no, check whether there is any problem with hc595O. Fault phenomenon: the upper and lower modules in the middle of the cell (the cell board is divided into upper and lower cells) are lack of red and green, or they are lack of red and green from the beginning to the end of the cell1. Visually check whether the integrated circuit corresponding to the fault on the unit board, such as hc595, has false soldering, short circuit and open circuit; If so.
the results show thatWeld the pins well.
22. Check whether the 5V power supply is normal.
check whether the 5V power supply is normal3. Use a multimeter to measure whether the voltage of 14 pins of hc595 input corresponding to the fault is normal; If so, judge that hc595 is broken (under other normal power supply conditions), and replace it with the same type of integrated circuit; If not, check the 9-pin output voltage of the corresponding hc595 and whether the circuit connecting wire is disconnected. If not, it is judged that hc595 is broken, and replace it with hc595 IC of the same model (pay attention not to disconnect the circuit lead when replacing the IC hc595).
if not, the hc595 is brokenOutdoor (module) maintenance instructions1. If the LED of the module is not on, it indicates that there is no power input. Please check the power supply part (which can be checked with a multimeter). If there is any color (bright spot with color confusion), it indicates that there is no signal input, Please check whether the input end of the first abnormal module's cable is in close contact. It can be plugged and unplugged for many times. If the problem still exists, you can replace the cable with a new one.
if the problem still exists, please check whether the input end of the first abnormal module's cable is in close contact2. Single mode group does not light up: check whether the power supply of the module is in good condition.
the main purpose is to check whether the power socket on the module is loose.
if the color of the whole module is confused or inconsistent (but there is a signal input.
there is a correct picture), it means that the signal transmission platoon is in poor contact and the platoon cable is plugged in again, Or replace the tested cable.
if the good cable is replaced, it still has the same problem.
please check if there is any problem with the PCB interface.
please check if there is any problem with the PCB interface3. Detection method for single lamp failure: use a multimeter to check whether the LED is damaged.
the LED is damagedIf the lamp is broken, change the lamp according to the following item 5.
specific method of measuring the lamp: turn the multimeter to the resistance x1.
the black pen of pointer multimeter is connected to the positive pole of LED, and the red pen is connected to the negative pole (the black pen of digital meter is connected to negative pole, and the red pen is connected to positive pole). If the LED is on, the measured lamp is good, if the lamp is not on, the measured lamp is bad.
if the LED is on, the measured lamp is good4 LED bad point maintenance (out of control point): after single lamp detection, it is confirmed that the LED is damaged.
according to the actual demand, the following maintenance methods are selectively adopted.
according to the actual demand4-1 front maintenance: remove the screws of the fixed mask from the front with the corresponding type of screwdriver (note that the screws are reserved).
remove the lower mask and change the lamp (please change the lamp according to the following method). After changing the lamp and sealing the gel, restore the original mask, tighten the screws (please pay attention not to press the lamp when installing the screws), and finally remove the gel carefully if there is any gel residue on the LED surface.
after changing the lamp and sealing the gel, remove the gel4-2 back maintenance: remove the screws from the back with the corresponding type of screwdriver (note to keep the screws).
unplug the signal cable. For safety, please do not unplug the power cable to prevent accidents. Carefully remove the module from the sheet metal hole and move it to the back of the box, Then, according to the front maintenance method, maintain the single module, change the lamp (please change the lamp according to the following method) or repair others5 lamp replacement: remove the colloid around the damaged led with sharp tools (such as tweezers).
and make the LED pin clearly show in sight. Clamp the LED with tweezers in the right hand, and touch the solder with soldering iron in the left hand (the temperature is about 40 degrees, too high temperature will cause damage to the LED), and stay for a little time (no more than 3 seconds, if the time exceeds, it does not meet the disassembly requirements, Please try again after cooling.) melt the solder and remove the LED with tweezersInsert the qualified LED lamp into the hole of PCB correctly.
(the long pin of the LED lamp is the positive pole, the short pin is the negative pole, the "square hole" on the PCB is the positive pin jack of the LED, and the "round hole" is the negative pin jack of the LED). Melt a little solder wire and stick it on the soldering iron head, adjust the direction of the LED with tweezers to make it stable, and solder the led to the joint of the LED and PCB, Use the same type of gel (pH=7) to seal the LEDFull screen fault:A. The whole screen is not bright (black screen)1. Check whether the power supply is on2. Check whether the communication line is connected.
whether there is a wrong connection.
(same step screen)3. The synchronization screen detects whether the communication green light of the sending card and the receiving card flashes4. Whether the computer monitor is protected.
or whether the display field is black or pure blue.
(same step screen)B. The whole unit board is not on (black screen)1. The transverse direction of several consecutive boards is not bright.
check whether the connection between the normal unit board and the abnormal unit board is connected; Or if the chip 245 is normal,2. The longitudinal direction of several consecutive boards is not bright, check whether the power supply of this train is normal.
the power supply of this train is normalC. The unit board does not light up1. Check whether the line pin is connected to the 4953 output pin.
check whether the line pin is connected to the 4953 output pin2. Check whether 138 is normal3. Check whether 4953 is hot or burnt4. Check whether 4953 has high level5. Check whether the 138 and 4953 control pins are connectedD. Unit board does not light up1. Check whether 595 is normal2. Check whether the corresponding pins of the upper and lower modules are connected3. Check whether the 595 output pin is connected to the module pinE. Lack of color in unit board1. Check whether the 245 R.G data has output2. Check whether the normal 595 output pin is connected to the abnormal 595 input pin.
check whether there is any connection between the normal 595 output pin and the abnormal 595 input pin1. Detect whether there is a short circuit between signals a, B, C and D.
the system can detect the short circuit between signals a, B, C and D2. Check whether the output terminal of 4953 is short circuited to other outputs.
check whether the output terminal of 4953 is short circuited to other outputsE. When all lights are on, there are single or multiple points (irregular) that are not on1. Find out whether the control pin corresponding to the module is short circuited to the line.
check whether the control pin is short circuited to the line2. Replace the module or single lamp.
replace the module or single lampF. When all lights are on, one or more columns are not on1. Find the pin that controls the column on the module.
test whether it is connected with the output of the driver IC (74HC595 / TB62726).
check whether it is connected with the output of the driver IC (74HC595 / TB62726).
check whether it is connected with the output of the driver IC (74HC595 / TB62726)2. Visually check the module pins and integrated circuits corresponding to the faults on the unit board for false soldering, short circuit and open circuit; If yes.
solder the pins.
If yes, solder the pins3. Measure the output of hc595 with a multimeter74HC04 74HC 245 74HC 138 74HC 595 74HC 4953 16126 RMB 0.5/piece RMB 0.65/piece RMB 0.55/piece RMB 0.35/piece RMB 0.75/piece RMB 1.9/pieceControl system1. The whole screen doesn't light up or squares appear? Control whether the host is turned on? Is the communication line plugged in? Is the sending card plugged in? Whether the data line between the multimedia card and the acquisition card is well connected? The switch position of JP1 or JP2 of receiving card is not correct? Turn on the host? Plug in the communication cable? Re insert the sending card? Connect the data line between the multimedia card, the acquisition card and the sending card? Adjust the switch position of JP1 and JP2? Is the computer monitor protected,Or the display area is black or pure blue.
(step screen)2. Every time you start the LED studio, you will be prompted that the signal acquisition line between the COM port of the control system and the data sending card is not found, or the COM port of the computer itself is broken.
connect the data line or replace the computer3. Whole screen shaking or ghosting? Check the communication line between the computer and the large screen? Check the DVI cable between the multimedia card and the sending card.
the DVI cable between the multimedia card and the sending card should be checked? The transmitter card is broken.
"re insert or replace the communication cable, punch in the DVI cable and replace the transmitter cardDriving part1. The first unit board doesn't light up?+ Is 5V power or GND supplied?+ Is there a short circuit between 5V and GND? 138 is there any OE signal of the fifth leg? 245 whether the connected OE signal is normal (open circuit or short circuit);? Power on + 5V or GND? Disconnect the short circuit? Supply the OE signal? Connect the open circuit and disconnect the short circuit2. The upper part or lower part of a unit board is not bright or the display is abnormal? Whether there is OE signal in the fifth leg of 138;? Whether the signal of leg 11 and 12 of 74HC595 is normal (SCLK, RCK)? Whether the connected OE signal is normal( Open circuit or short circuit)? Whether the SCLK and RCK signals of double row pin and 245 are normal( Open circuit or short circuit)? Connect the OE signal? Connect the SCLK and RCK signals? Connect the open circuit and disconnect the short circuit? Connect the open circuit and disconnect the short circuit3. A line on a unit board or the line of a corresponding module does not light up or displays abnormally? Check whether the pin of the line signal of the corresponding module has false soldering or missing soldering;? Check whether the pin corresponding to the line signal and 4953 is disconnected or short circuited with other signals? Check whether the up and down resistance of the line signal has no welding or missed welding? Is the line signal output from 74HC138 disconnected from the corresponding 4953 or short circuited with other signals? Weld the false and missed ones well? Connect the open circuit and disconnect the short circuit? Mend the missing and weld the missing? Connect the open circuit and disconnect the short circuit4. Two lines of a unit board are on at the same time (one line is normal and the other line is always on when the text is displayed)? Check whether the two lines of signals corresponding to the module are short circuited? Check the output leg of 138, up and down resistance, module pin and 4953 for short circuit? Disconnect the short circuit5. The upper part or the lower part of the red or green is not bright or abnormal display? Check whether the input row pin is normal or short circuited to GND, + 5V? Check whether the signal between the input row pin and 245 is normal (short circuit or open circuit)? "Ic245 is broken" connect the circuit breaker? Disconnect the short circuit? Replace ICSystem troubleshootingStep 1: check whether the graphics card setting part is set wellThe setting method can be found in the CD-ROM electronic file, please refer toStep 2: check the basic connection of the system.
for example, whether the DVI cable and network cable socket are correct, the connection between the main control card and the computer PCI socket, the connection of the serial port cable, etc. the connection method has been illustrated, please refer to it carefullyStep 3: check whether the computer and LED power supply system meet the use requirements.
when the LED screen power supply is insufficient.
when the display is close to white (high power consumption), the screen will flash, and the appropriate power supply should be prepared according to the power supply requirements of the box.
when the display is close to white (high power consumption), the screen will flashStep 4: check whether the green light of the sending card flickers regularly: turn to step 6 if it flickers.
if it does not flicker, restart and check whether the green light flickers regularly before entering WIN98 / 2K / XP. If it flickers to step 2, please check whether the DVI cable is connected well. If the problem is not solved, please replace the sending card, the video card and the DV cable I and repeat step 3Step 5: please set it according to the software instructions or re install it before setting it.
until the green light of the sending card flashes, otherwise, repeat step 3.
Step 3Step 6: check whether the green light of the receiving card (data light) flashes synchronously with the green light of the sending card.
if it flashes, turn to step 8 to check whether the red light (power supply) is on; if it is on, turn to step 7 to check whether the yellow light (power protection) is on; if it is not on, check whether the power supply is connected reversely or there is no power output; if it is on, check whether the power supply voltage is 5V; if it is off, remove the adapter card and cable and try again, If the problem is not solved, replace the receiving card and repeat step 6.
the receiving card is faultyStep 7: check whether the network cable is well connected or too long (the standard super class 5 network cable must be used.
the maximum distance of the network cable without repeater is less than 100 meters), and check whether the network cable is made according to the standard (please refer to the system installation and setting),If the problem is not solved, replace the receiving card and repeat step 6.
the receiving card is faultyStep 8: check whether the power light on the large screen is on.
if not, turn to step 7 to check whether the adapter card interface definition line matches the unit board.
if not, turn to step 7Note: after most screens are connected.
there may be no picture or flower screen in a local box. Because the RJ45 interface of the network cable is not firmly connected, or the power supply of the receiving card is not connected, the signal is not transmitted, so please re plug the network cable (or replace it), or plug in the power supply of the receiving card (pay attention to the direction)Abnormal displayI. the whole screen is not bright (black screen)1. Check whether the power supply is on.
check whether the power supply is on2. Check whether the communication line is connected.
whether there is a wrong connection.
(same step screen)3. The synchronization screen detects whether the communication green light of the sending card and the receiving card flashes4. Whether the computer monitor is protected.
or whether the display field is black or pure blue.
(same step screen)II. The whole unit board is not on (black screen)1. The transverse direction of several consecutive boards is not bright.
check whether the connection between the normal unit board and the abnormal unit board is connected; Or whether the chip 245 is normal.
or not2. The longitudinal direction of several boards in succession is not bright.
check whether the power supply of this train is normal.
check whether the power supply of this train is normalIII. The unit board does not light up1. Check whether the line pin is connected to the 4953 output pin.
check whether the line pin is connected to the 4953 output pin2. Check whether 138 is normal3. Check whether 4953 is hot or burnt4. Check whether 4953 has high level5. Check whether the 138 and 4953 control pins are connectedIV. the unit board is not on1. Check whether 595 is normal2. Check whether the corresponding pins of the upper and lower modules are connected3. Check whether the 595 output pin is connected to the module pinV. lack of color in unit board1. Check whether the 245 R.G data has output2. Check whether the normal 595 output pin is connected with the abnormal 595 input pinGraphics card settingsThis description only takes ATI's radium series 9550 computer graphics card as an example.
if you use other graphics cards, please use this as a reference for debugging.
note: there are three settings in the graphics card setting section.
and you must meet the.
: 2.
3 options in the graphics card driver software, so you must install the appropriate graphics card driver software1 screen refresh rate must be 60Hz, otherwise no screen display2. The display options need to be in "copy" mode3. In the display options of the graphics card, there should be an item "all the same" (video Cinema mode all the same in the drop-down menu of ATI 9550 in the graphics card condition software)Application of Circuit Foundation and common componentsWhat is a circuit?A circuit is a network composed of interconnected electronic and electrical devices, such as resistors, capacitors, inductors, diodes, triodes and switches.
the size of the circuit can vary greatly.
as small as the integrated circuit on a silicon chip, as large as the power transmission network.
according to the different signals processed.
electronic circuits can be divided into analog circuits and digital circuits.
according to the different signals processed, electronic circuits can be divided into analog circuits and digital circuitsAnalog circuits process the current and voltage of signals.
the most typical applications of analog circuits include: amplification circuit, oscillation circuit, linear operation circuit (addition, subtraction, multiplication, division, differentiation and integration circuit). typical digital circuits are.
oscillator, register, adder, subtracter, etcThe theoretical value of Voh in CMOS gate circuit is the supply voltage VDD.
Voh (min)=0.9vdd; The theoretical value of vol is 0V, and Vol (max)=0.01vdd.
therefore, the logic swing of CMOS gate circuit (i.e. the difference between high and low levels) is large.
it is close to the VDD value of power supply voltage.
the theoretical value of Vol is 0V, and Vol (max)=0.01vddTTL gate level:The output high level is more than 2.4V.
the output low level is 2.0V, the input low level is less than 0.8V, and the noise tolerance is 0.4VOpen / open circuit: the current does not form a loop in the circuitShort circuit: the current does not directly pass through the load normally.
but passes through a small resistance object in parallel with the load, and the object is not within the electrical range of the design circuit, which is caused by other reasons. The phenomenon of connection is called short circuit.
conscious short circuit will not cause the normal operation of the circuit.
unconscious short circuit will damage the circuit and even cause it to fail to work normally.
short circuit is a kind of phenomenonDC (voltage / current): the phase of voltage / current will not change with timeAC (voltage / current): the phase of voltage / current changes with timeConstant current: the current will not change with the loadConstant voltage: the voltage will not change with the loadDigital signal: only high / low level appears.
what the computer processes is digital signal, so is our LED display. Generally, high level is represented by "1" or "H",The low level is represented by "0" or "L.
the data is represented by binary, octal and hexadecimal.
octal is less used.
we use decimal system in our daily lifeExample: binary (01010101)=octal (125)=hexadecimal (55h)=decimal (85)Binary (00000001)=decimal (1), binary (00000010)=decimal (2)Binary (00000011)=decimal (3)Current I: 0.001ka=1A=1000mA=1000000uaVoltage U: 0.001kv=1V=1000mV=1000000 UVResistance R: 1m Ω=1000K Ω=one million Ω Capacitance C: 0.001f=1uF=1000nf=1000000pfOhm's Law: I
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