The 90M10-AG is a non-invasive clamp-on sensor that requires kV to be in beam. The mAs sensor connects to the 4-pin connector labeled mAs using a 4-m cable and couples to the X-ray generator by clamping to the X-ray anode HV cable (clamps up to 23 mm in diameter). The value of mAs is computed by summing mA values during the part of the kV waveform (requires kV sensor in beam) defined by the same thresholds that are applied to determine its width, generally 75% of kVp. To measure the anode current, clamp on the anode cable with the arrow on the clamp pointing towards the X-ray tube.
Key Features
- Automatic power control extends battery lifetime
- Automatic zero
- Measurement synchronized to kV waveform
- Maximum 9999 mAs and 0.7mA (RMS noise) to 2A dynamic range with no range switching
- Measures absolute value (no rectifier drop and optimum noise rejection)
- Measures absolute value of mA
- mA-waveform
| Specification / Technical Data | |
| Range | 1900 mA or 9999 mAs (2-2000 mA when used with 9095) |
| mA accuracy | ±4% of reading (Limited by 0.7mA RMS noise below 18mA) |
| mAs accuracy | ±4% of reading (Limited by 0.7mA RMS noise below 18mA) |
| Bandwidth | 2.33 kHz, -3 dB |
| ON/OFF | ON/OFF controlled from Accu-Gold, Accu-Pro/Accu-kV (ON only when a kV function is active) |
| Batteries | 2 x IEC-LR6 (1.5V AA Alkaline) Lifetime: Approximately 35 continuous operating hours |
The sensor responds to the net current passing through the opening. This means that current flowing in the cable shield can add or subtract from the tube current. To a lesser extent, nearby electrical circuits can also affect the measurement, as can the motion of the cable within the clamp opening. The instrument program compensates for the effect of these extraneous signals by continuously measuring the sensor output and computing a zero correction. When a measurement begins the mostrecent zero measurement is stored and used to correct the reported value. This correction is limited to 50 mA; if the zero is larger than this value a measurement error occurs. Extraneous signals are generally not a problem for tube currents above about 100mA.
For measurements where errors in the 5 mA range are significant, Radcal recommends the following:
- Position the sensor on the anode cable so the cable doesn’t move relative to the sensor.
- Locate the sensor away from magnetic noise sources, particularly those that might change during the exposure because the zero correction is measured several seconds before the exposure. The tube rotor in particular could be a problem.