Milwaukee True RMS Fork Meter 2205-20 Review:
The following are some of the features of the milwaukee true rms fork meter 2205-20.
It is a two stage fork meter with a red LED light at each end. It measures both forks simultaneously. A single push button on top allows you to measure either one or both forks independently. The measurement range is 0 to 20 volts DC (0 to 5 volts AC).
It measures current at the voltage rails. Current is measured from the positive rail to ground and from negative rail to ground. There are no measurements made between the voltage rails.
There are three LEDs located on top of the meter which indicate whether it is measuring current at one or both ends of the forks. Two LEDs illuminate green when current is being measured at the positive rail and red when it is being measured at the negative rail.
The third LED indicates that there is not enough power available to complete all measurements. If this happens, then the meter will continue to display “Not Enough Power” until sufficient power becomes available.
When the meter displays “Not Enough Power”, you may need to increase your battery charge level in order for it to work properly again. To check the charge level, press and release the mode button. If the display reads “Charge Low”, then it is time to recharge it.
If there is no display illumination, then make sure that the power save feature hasn’t kicked in. The meter has a built in power save feature that kicks in after about a minute of non-use. You can turn this feature off by pressing and holding in the mode button for two seconds. The display will turn on.
The backlight turns off automatically after about a minute of non-use. You can turn the backlight on by pressing and releasing the mode button.
There are several ways to turn the power off. You can let it sit for a few minutes with no activity. This will cause the power save feature to kick in and turn it off. You can also press and hold in the mode button for two seconds. The display will turn off.
This meter can be affected by strong electro-magnetic fields. This can cause erratic or inaccurate readings. You should avoid operating this meter near magnetic fields.
The meter is factory set to display the least significant digit first (either decimal or fraction). For example, if the voltage displayed is 2.00 volts, then 200 milliamps are flowing through the forks (200mA x 0.01 = 2). If the voltage displayed is 1.00 volt, then 10 milliamps are flowing through the forks (10mA x 0.01 = 1).
You can change the display depending on your preference. Turn the fork tines so that they are parallel to each other and press and release the mode button. The least significant display digit will blink. Press again until you get the desired setting. If you make a mistake or change your mind, just keep pressing the mode button until you get back to the display you had before.
The fork tines are designed to fit onto the terminals of most batteries. If the forks do not make good contact with the battery terminals, then the current drain will not be correctly measured. This may result in the display not showing any current when in fact a large current is actually flowing (or conversely, showing milliamps when only microamps are flowing).
If you find this happening, you should try to make better contact between the battery terminals and the fork tines. You can also try temporarily removing the battery from the device and holding the forks directly against the battery terminals while measuring. The display will show a large number (greater than 5mA). Try to make sure the forks are pressed tightly against the battery terminals while making this measurement. The display will go back to what it was previously after a few seconds.
If you want to be sure that large currents are not flowing through the meter, then you can place the meter in series with the load. This is done by connecting the positive side of the battery to one set of tines and connecting the negative side of the battery to the other set of tines. The current will then flow through the meter and be calculated as usual.
The display shows a negative sign before the decimal point if the current is flowing the opposite direction of what it should be. For example, if you connect the meter backwards by connecting the positive side to the negative terminal and the negative side to the positive terminal, then the display will show a negative value but still display the same number of decimal places (e.g. 3.141592 instead of 3.14159).
The display will show “ERR” and no current reading will be taken if the fork tines are not making good contact with the battery terminals.
The following table lists all the possible displays and what they correspond to in real units.
0.000xx microamps (e.g. 0.00027) 1 microamp 0.00xx microamps (e.g.
0.004) 2 microamps 0.0xx microamps (e.g. 0.026) 3 microamps 0.xx microamps (e.g. 0.12) 4 microamps 0.x microamps (e.g. 0.8) 5 microamps 1.x microamps (e.g. 1.3) 6 microamps xx microamps (e.g. 1.9) 7 microamps xxx microamps (e.g. 2.7) 8 microamps xxx microamps (e.g. 3.4) 9 microamps xxx microamps (e.g. 4.1) 10 microamps
mili (thousandths of an amp) nn (decimal point, no number after) nnn (2 decimal places, e.g. 0.00372)
z (2 decimal places, e.g. 3.141592) zz (3 decimal places, e.g.
ffff (4 decimal places, e.g. 3.14159265) ffff (5 decimal places, e.g.
Using the Multimeter to Check a 9-Volt Battery
This little experiment will give you some idea of what the different readings mean. Take a new 9-volt battery and your multimeter and measure the voltage in fresh water (not sea water). Set the meter to the 20V range if it has such a setting. Record this reading in your lab book. Next, measure the voltage of the same battery in sea water.
Record this reading as well.
A battery that is fresh from the store has a voltage of around 1.6 volts, when placed in sea water, this voltage decreases. This decrease is caused by a chemical reaction that is going on inside the battery as it produces electricity. You can think of a battery as a little container of sea water in which a chemical reaction is taking place between the electrodes and the electrolyte (the sea water). The electrodes are made of different metals which act as electron donors.
In the case of a 9-volt battery, the metal “cathode” (which is hooked up to the positive terminal of the battery) gives up electrons. The other metal “anode” (which is hooked up to the negative terminal of the battery) accepts these electrons. This process goes on and on and electrons flow from the cathode to the anode through a wire, doing work along the way. If you place a magnet next to the cathode and move it away, the electrons will flow in straight line from the cathode to the anode and soon stop because the magnet has stopped moving. The cathode is usually half magnesium and half copper.
Magnesium is a metal that gives up its electrons easily. Copper is a metal that accepts electrons easily. The magnesium and copper electrodes start out looking like little metal pellets. When the battery is placed on the market, these little pellets are poured into the container along with sea water and a seal is put on top of the container. When this reaction takes place, it produces electricity and also transforms some of the magnesium into a new substance called magnesium hydroxide.
The magnesium hydroxide is not really necessary for the battery to produce electricity so it can be ignored in this discussion. The important thing to remember is that the magnesium converts some of its mass into electrons and becomes magnesium hydroxide, and the copper converts some of its mass into electrons and becomes copper hydroxide. The magnesium hydroxide remains in the container because it is not very soluble in sea water. Most of the copper hydroxide remains in the container as well. Some of it does dissolve into the water.
Sources & references used in this article: