Power Measurements
A device, sometimes called an "amp clamp", can be used to measure the AC current flowing in a wire. It is not necessary to connect the device to the electrical circuit that contains the wire. It is necessary only to pass the wire through the jaws of the device. For the device to work the wire that passes through its jaws must contain only one wire from an AC circuit. If an entire electical cord is used then the current in one branch of the cord will cancel the current in the other branch. Instead a short extension cord is used in which one branch is separated from the other. For devices in which the current is small (and therefore difficult to measure) it is possible to wrap the cord around the jaws of the device several times to multiply the reading (if wrapped 3 times the reading is 3 times larger than the actual current)
The power drawn by any of the equipment in the racks depends somewhat on the number of interfaces installed in the equipment. For example, a LANplex 2500 with no interfaces may draw less than 0.5 amps, but one with all four interface slots filled may draw 0.75 amps. The chart below shows the current ranges typical of the devices in the racks.
| DEVICE | CURRENT RANGE |
| Computer + Monitor | 1-1.4 amp |
| Xyplex Maxserver 1600 | 0.16 amp |
| Asante AH2072 | 0.75 amp |
| Cisco 2900 | 0.6 amp |
| Cisco 4000 | 0.75 amp |
| Cisco 7000 | 3.0 - 6.25 amp |
| Cisco 7010 | 3.25 amp |
| 3COM 3LANplex 2500 | 0.75 amp |
| 3COMCorebuilder 3500 | 1 amp |
| 3COM Cellplex 7000 | 1.25 amp |
Some of the devices have redundant power supplies. This is most evident for the Cisco 7000s. The current drawn by such a device when both power supplies are plugged in is approximately the same as the current drawn with a single power supply. The power drawn by a computer depends on whether it is idle. Power consumption increases when programs are running which use the disk or the CPU intensively.