5
Exposure Time Measurements:
The exposure time will be displayed in milliseconds (ms).
mA Lead Connection
The mAs meter was designed to be connected in the ground return line of the high
voltage transformer and must be in the actual current path of the x-ray tube. The
meter can be connected in series with the rectified tube current (DC Path), via the
DC input jacks or it can be connected using the AC input jack in series with the
transformer downstream of the rectifier (AC Path). However, all tube current must go
through the mAs Meter to have an accurate reading. If an alternate or parallel
current pathway of the x-ray generator is present, it could bypass the meter and
invalidate the reading. Do not use resistors, varistors, bypass, or distributed
capacitors in parallel with the meter. This will affect calibration. Before using the mAs
meter, examine the circuit of the x-ray generator and be certain that the mAs meter
is connected so that such components will not affect the readings. Varistors, which
have limiting voltage above 10V, will probably not affect the reading.
STATUS MESSAGES
Applies to kVp and mA Measurements
The alphanumeric display on the Model 870 is capable of displaying messages
along with the output readings that give the user additional information. Each
message is described below:
Rdy 2A- Unit is ready for a reading in the 2 Amp range.
Rdy 200mA- Unit is ready for a reading in 200mA Range
Over Range - Over Range. The x-ray output is too high. Switch to 2 Amp range.
Low Battery - Battery is low. The unit may still be operated for several hours, but
accuracy may suffer. Replace the batteries as soon as possible.
BATTERY REPLACEMENT
The Model 870 is supplied with one 9V battery. Replace the battery when the "Low
Battery" indication shows in the display. Any standard 9V batteries can be used in
the 870. We recommend Duracell MN1604 9 Volt Alkaline Battery To prolong
battery life, turn the instrument off when not in use.
To replace the battery, open the battery compartment on the bottom of the case
using a small screwdriver or thumbnail. Remove the old batteries, and install the
new batteries. Observe the correct polarity of the battery as shown on the bottom of
the battery compartment.