External Battery Operation
with R-506 and R-507

Technical Note

By: Engineering Staff

Z Technology, Inc.

111013 1000  data subject to change without notice 

In response to customer feedback, we believe it would be helpful to provide a more detailed explanation on how to operate the R-506 and R-507 Field Strength Meters from an external battery or other external power source.

DC power may be applied via one of two power connectors on the rear panel of each instrument. Each power input has somewhat different characteristics and each is designed for a unique purpose. Both inputs employ the same connector type. The connector labeled “Auxiliary Power” is for an external (~8 to ~11½ VDC) battery pack, and the connector labeled “External Power Supply” is for an external (~12 to ~20 VDC) power supply.

"Auxiliary Power” Input
In the center of the rear panel is an external battery input connector labeled “Auxiliary Power”. The “Auxiliary Power” connector allows a second battery pack, (~8.0 to ~11.5 VDC) to be used with a Z Technology instrument. The connector is wired so that the center pin should be connected to the positive (+) terminal from the external battery. This “Auxiliary Power” input is provided for operators wanting to do extensive field-testing requiring several hours of operations from batteries. When the proper external battery pack is connected at this port, an instrument will be able to operate for extended periods and will draw power from both internal and external battery packs. Each pack will be used and eventually discharged as current is drained from both sources.

Field strength meters contain internal rechargeable batteries configured into a pack of eight (8) ‘C’ cells wired in series. Depending on the condition of charge, the internal pack will have a voltage of between approximately 8 volts and 10 volts DC. Both internal and external battery packs can be recharged from an R-506/R-507 meter when an external power cube is used as described in the “External Power Input” section below. Power applied to the “Auxiliary Power” connector will not recharge the instrument’s internal battery. The “Auxiliary Power” input is designed to protect the internal circuitry of the R-506/R-507 from voltages that are above ~11.5 VDC. If the external DC voltage at the Auxiliary Power connector is greater than ~11.5 volts, it will be electronically disconnected and no power will be drawn from the external battery. The “Auxiliary Power” input will also disconnect if external voltage falls below ~ 8 VDC to protect an external battery from excessive discharge and possible cell reversal ⁽¹⁾.

What About Battery Discharge
When using rechargeable batteries, another issue must be considered. There is a limit beyond which it is no longer healthy to continue drawing current from a partially discharged battery. The R-506/R-507 meters use an internal voltage sensor along with its microprocessor to determine when to power-down (auto turn-off) the instrument. This is necessary for battery-operated instruments in order to have a safe shut down of the microprocessor and a subsequent orderly next power-up cycle. Z Technology’s meters include a low-battery warning feature. When a battery pack (either internal or external) reaches a certain point in the discharge cycle, the meter generates a front panel flashing signal to alert the operator. The front panel LCD will display the letters “BATT” as battery voltage begin to sink below a specific preset value. As the voltage continues to sag even further, the “BATT” signal will begin to slowly blink. The closer an instrument moves to the automatic shut down sequence, the faster the blinking will occur.

In Z Technology’s instruments the DC voltage level is usually set so that the meter will automatically shut down at the point where the voltage of the internal battery falls below ~7.5 V, and the DC voltage at the “Auxiliary Power” connector falls below ~ 8 volts ⁽¹⁾. Below these points both battery pack voltages are too low to be usable. From an external voltage of ~ 8 volts up to ~ 9 volts, with the internal battery discharged, a “BATT” warning indication will be displayed on the LCD screen. Therefore, the lowest voltage where a meter will continue to operate from an external battery in a fully calibrated mode is ~ 8 volts. Above ~9 volts no warning is displayed or is needed. Let’s summarize both upper and lower limits for the “Auxiliary Power” input connector. Voltages must be between the lower limit of ~ 8 volts and the upper limit of ~ 11.5 volts. Between these two points, the meter will operate properly and will utilize the external power source connected to this rear panel plug. Below ~ 8 volts the meter will operate from the internal battery or will shut off. If the voltage at the “Auxiliary Power” input is higher than ~11.5 volts this input automatically become an open circuit.

“External Power Input”
A second rear panel input is available as a power source for the instrument. It is labeled the “External Power Input” and is the DC input normally used to power the meter from an external power supply such as an AC to DC converter –sometimes called a power cube. This power cube can be used to both recharge the internal eight (8) ‘C’ cell battery pack and supply the instrument with all necessary current to operate. Most standard power supplies providing at least 1 amp at a voltage of from 12 volts – 20 volts DC will work nicely for this power source. (A power cube meeting these specifications comes with each instrument.) The meter rear panel shows a wire diagram for proper connection to this input plug. It should be noted that if an operator plans to power the R-506/R-507 from a car battery, this is the input to use since lead-acid car batteries typically have output voltages within this range.

This input serves a second important task. Only the “External Power Input” can be used to recharge the internal battery pack. It will provide a trickle charge that can easily recharge the internal battery pack over a 12-hour period. In fact, with a high enough current power cube connected to this input, an external battery pack attached to the “Auxiliary Power” plug also may be recharged. To charge both internal and external packs, simply connect both the power cube to the “External Power Input” and the external battery pack to the “Auxiliary Power” connector at the same time. The charging method for the external pack is the same as for the internal batteries.It will be trickle charged. The full recharge takes approximately 12 hours.

Which Power Source Goes Where?
As we have indicated, the two input power plugs look very much alike. So it can be confusing as to which plug should be use for different purposes. The good news is that you cannot damage the R-506/R-507 by accidentally plugging a power source into the wrong connection.

Here is a summary that will help keep things straight.

Note ⁽¹⁾: If this is not the case with your instrument, contact the factory for a firmware fix. (Some instruments were shipped with a DC voltage cut off set above the 8 volt level.)

Note ⁽²⁾ Both input connectors expect the center-socket of the connector from the external battery pack (or power supply) to be the (+) positive voltage terminal.

The Meter's built in Battery Voltage Check mode (F1)
The meter F1 function displays an uncalibrated battery voltage level.  It is a relative level of the power source that is powering the meter.  If the meter is running on only the internal battery the F1 display shows somewhere in a range from ~ 8.0 to 10.6 depending on the state of charge of the internal battery.  If the AC power cube is plugged in the voltage level rises to range ~ 10.8 to 11.2 again depending on the state of the internal battery, closer to the lower number ~ 10.8 if the battery is discharged, and in the charging mode, closer to the higher number ~ 11.2 if the internal battery is fully charged and healthy.  

There is a "Reset" switch in a recessed hole on the back of the meter next to the RS-232 connector.  Pressing the Reset switch disconnects the internal battery.  There are some interesting consequences of this when the meter is in F1 Battery Check mode.   

If the meter is running on internal battery power only then pressing the Reset switch will reset the meter.

If the meter is connected to its AC power cube, then a press and hold of the Reset switch does not reset the meter, but instead shows the internal voltage produced by the AC power cube without the drain of charging the internal battery. 

If the AC power cube is not connected but the External battery is connected to the "Auxiliary Power" input then a press and hold of the Reset switch shows the relative voltage level of the External battery.