Teledyne 4220 installation and operation guide Current Draw

4220 Flow Meter
Section 1	Introduction
		nickel-cadmium batteries show fairly rapid rates of self-dis-
		charge. A battery that is fully charged and then placed in storage
		will lose some capacity each day. In a week, this could easily be
		5% or more.
		When using lead-acid batteries, you must be careful to avoid
		complete discharge, as this may cause cell reversal, which will
		ruin the battery. Also, complete discharge in low temperature
		ambients may cause the battery to freeze, which can deform the
		plates or even crack the case. Always operate these batteries
		with a reserve factor!
1.7.1	Current Draw	Calculating current draw for a 4220 Flow Meter is somewhat
		more difficult than calculating the battery capacity. You cannot
		simply measure the idle current of the unit unless the printer

and report generator are turned off in the program. These functions require power periodically, but not all the time. If the figures given in the previous table are not satisfactory for your application, you can use the following procedure (shown in Figure 1-4)to measure the actual current draw.

Note

Do not attempt this procedure unless you have the proper equipment available and know how to make electrical mea- surements.

To measure current for a varying load requires a more-sophisti- cated type of multimeter, one that is capable of averaging high and low readings over a period of time. You should set the meter on MIN/MAX and let it run with your program for several hours or more. Other manufacturers’ meters are also acceptable, but only if they are capable of averaging current draw. For a more representative test, the area-velocity sensor should be attached and submerged in water. You should run the test for at least eight hours, longer if necessary, or until the flow meter has exercised the entire program. The longer you run the test, the more accurate the average will be.

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