Fluke Biomedical TNT 12000 - Manual (Page 68)

TNT 12000
Users Manual
2-40
Shunt Connections
You must put the mAs shunt in series with the actual current path of the x-ray tube. This
is usually the ground line of the high-voltage transformer of the X-ray tube. You can put
the shunt in series with the rectified tube current (dc path), through dc input jacks. A
different procedure is to use ac input jacks in series with the transformer downstream of
the rectifier (ac path).
It is necessary that all the tube current go through the mAs shunt to make an accurate
measurement. If different or parallel current path of x-ray tube current bypasses the
shunt, the measurement will be incorrect.
Do not use resistors, varistors, bypass, or distributed capacitors in parallel with the shunt.
The effect of these components can cause measurement errors. Before you put the mAs
shunt in the current path, examine the X-ray tube current circuit. Make sure that the shunt
is connected so these components do not have an unwanted effect on the measurement.
Varistors, which have limiting voltages more than 10 Volts, will probably not change the
measurement.
The mAs adapters shipped with the TNT 12000 adapt the shunt to different X-ray tube
mA/mAs connections. Some X-ray generators have standard 1.9 cm (0.75") spaced
banana jacks or binding posts to monitor X-ray tube current. After you remove the
shorting plug, the TNT 12000 shunt is connected to these jacks for mAs measurements.
As Figure 2-18 shows, the BNC Female to Banana Plug adapter connects the shunt to the
mAs input through the mA/mAs interface cable.
XW Warning
To prevent electric shock or personal injury, follow these
guidelines:
• Observe extreme caution when power is applied to the
shunt.
• Use this Analyzer only in the manner specified by the
manufacturer or the protection provided may be
impaired.
• Follow all safety precautions called for in the X-ray
generator documentation.
• Use extreme caution when working with voltages above
30 V.
• Inspect the test leads for damaged insulation or exposed
metal. Check the test leads for continuity. Replace
damaged test leads before you use the TNT 12000.
• Do not touch the test leads or the Detector while power
is applied to the circuit under test.
• Turn the X-ray generator off before connecting or
disconnecting the TNT 12000.
W Caution
To prevent damage to the TNT 12000 or equipment under test,
do not exceed 500 V peak between the input and earth ground.