Battery Operation; Connections; Thermocouple Connections - Ectron 1140A Instruction Manual

Applications

BATTERY OPERATION

Although operation from either ac power or battery makes virtually no difference to the user,
there are some precautions that should be observed. The battery pack is of the nickel-metal
hydride (Ni-MH) type which, unlike Ni Cad batteries, should never be allowed to discharge
completely. Fortunately, the sophisticated charger circuitry used in this instrument prevents this
from happening.
To charge the battery pack optimally, its temperature is continuously monitored. In addition, if its
temperature is outside of recommended limits charging is not allowed. Two charge current levels
are incorporated. The first is a high-rate charge allowing a three-hour charge time. The second is
a lower charge current used to "top off" the battery.
This battery pack can be given a partial charge when necessary although a full charge period
should be used periodically to preserve optimum battery life.
Another very important characteristic of the Ni-MH battery is that it should be recharged at least
every two months to obtain maximum life. Normal performance can be obtained from the battery
over the full temperature range of this instrument: 0°C to 50°C.
For details of the battery-related messages that may appear in the display of the Model 1140A,
see Message Displays

CONNECTIONS

Binding posts and a mini-three-pin thermocouple connector are provided for source and measure
connections. Four temperature sensors embedded in the front-panel terminals, two in the mini-
thermocouple connector and two in the binding posts, allow the Model 1140A to compensate for
ambient temperature variations. Despite Ectron's best efforts to minimize errors at these
terminals, certain thermal conditions can cause measurable errors in both measure and source
modes.

Thermocouple Connections

When using thermocouples, the choice of either the binding posts or the mini-connector is up to
the user and the application. However, better performance sometimes can be obtained using the
binding posts, because their higher thermal mass allows better sensing within each terminal. This
would only be a concern when highest possible accuracy is required and ambient conditions are
poor.
For instance, if local conditions include variable air temperature such as operation on a flight line
and in addition highest accuracy is required, then slightly more stable results may be obtained
when using the binding posts.
CAUTION
The battery pack, if installed, must be charged at
least once every two months. If this is not done, the
battery-pack voltage may decay beyond its ability to
recover.
in the Operation section.
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