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Product FAQ

The quickest and easiest way to find answers to your questions is searching our Frequently Asked Questions by product.

If your question is not included in our FAQ yet, please contact our Support Team and help us to improve our FAQ list for future use.

What is the difference between R/F high and R/F low, and how do I use them?

R/F low is optimized for low signal levels, typically found during fluoroscopy, behind a phantom. It has a high sensitivity at the cost of a lower bandwidth (0.1 kHz) and should be used at dose rates below approximately 1 mGy/s. R/F high is optimized for higher signal levels and features a higher bandwidth (2.5 kHz). It is typically used before a phantom, and is required for measuring kVp (as opposed to kV).

What is the difference in dose and dose length product in a CT application?

Dose is basically a property of a point in space, while dose length product (DLP) is dose times a length. When measuring with a 100 mm ionization chamber the following holds true: DLP = (Measured dose in a point and assuming a homogenous field) • (Slice Width). When using the RaySafe Xi CT it is possible to change between Dose and DLP by selecting Dose Unit as Gy or Gycm in the settings menu.

How do I switch between kV and kVp?

The RaySafe Xi switches to kVp automatically, as soon as the signal level is high enough (but only when using R/F high). For high frequency generators, the difference between kV and kVp is negligible.

In comparison to an ion chamber, the RaySafe Xi shows lower values, why?

The RaySafe Xi R/F or Mammography Detector only measures radiation from one (1) direction, not scattered radiation from behind, because the back of the detector is shielded with 1 mm of lead. The detector may therefore be placed on any surface and still measure true air kerma. Most ionization chambers measure primary as well as scattered radiation, which is why they should be placed free in air (at least 0.5 m (2 ft) from any scattering material). When used in such fashion, the RaySafe Xi will show similar readings when compared to an ion chamber.

What is the difference between the “paddle” and “no paddle” setting in the Mammography sensor menu?

The setting is to be able to measure accurate kV with and without the compression paddle in the field. This setting selects between two different kV calibrations. It does not affect any other measurement, such as dose, HVL or time.

Why do I not get a kV reading when choosing beam qualities other than Mo/Mo (and optional: Mo/Rh, W/Rh and W/Al) for mammography?

As far as we know, all mammography devices have at least one of the above mentioned beam qualities. It is enough to measure kV for one (1) beam quality on each machine since the true kV is the kV over the x-ray tube and not the result in the x-ray beam after filtration. To calibrate the RaySafe Xi for measuring kV on other beam qualities would thus result in unnecessary complexity and a higher calibration cost.

What happens if the mAs cable is connected with the wrong polarity?

The RaySafe Xi will not show any mAs readings. As long as the mAs cable is securely connected to both generator and base unit (in any polarity), there is no increased risk of damaging the generator or the Xi.

When turned on, the RaySafe Xi briefly shows “Battery down” and refuses to start.

Please charge the battery, see chapter Getting Started in your Xi Manual.

Values do not show up in RaySafe Xi View

Make sure that all cables are properly connected and that you have:
• If using Bluetooth, established a Bluetooth connection (password 1234).
• If using serial cable or USB/Serial adapter, select the correct COM port in file/settings menu of RaySafe Xi View.
• press the RaySafe Xi View Communication Start button.

The RaySafe Xi shows only half of the expected mAs value.

If you are measuring on a generator with AC signal on the mAs measurement point, you will need a rectifier (optional) to get correct values. Contact Unfors Technical Support.

When the RaySafe Xi with CT Detector is turned on, the instrument displays “Offset out of range” after displaying “Stabilizing.. ” for a long time.

This means that the ionization chamber current fails to reach a stable level when the instrument is turned on. Please make sure that:
• the chamber is not irradiated during stabilization or zero adjust.
• you are not operating the instrument outside its specified temperature range. If the problem persists, your instrument might be in need of a repair. Please contact Unfors Service department.

I get Zero adjust out of range

Make sure that:
• you are not operating the instrument outside its specified temperature limits.
• you are not irradiating the detector during the zero adjust phase (when values on display are blinking). When used with pulsed sources it may be necessary to select a longer Calc. delay to avoid end trig and zero adjust during the measurement (see also next problem).

The RaySafe Xi R/F or Mammography Detector end trigs during exposure.

Make sure to select an appropriate Calc. delay if using the instrument with pulsed generators, or with generators having a pre-pulse before the main exposure. The Calc. delay is the time the Xi will wait after radiation before finishing the measurement.

The RaySafe Xi does not respond when pressing keys.

Try the reset switch and make sure that the battery is charged. The reset switch may be found on the LEFT side of your Xi Base unit by accessing the small, unlabeled hole adjacent to the Serial cable. Gently insert the exposed end of a paper clip into the aperture ONE TIME. The Xi Will turn OFF, and reset. Please press the ON key on your Xi front panel to reactivate the Xi.

I get strange mAs readings when I’m using the RaySafe Xi’s AC adaptor or when my computer is connected to mains power.

Make sure that the instrument was connected to the generator during "Zero Adjust" *
• is operating on battery (no AC adaptor). *
• is not connected to a grounded computer (use Bluetooth or a laptop running on batteries with no Ethernet cable connected).

* = Valid for Xi Platinum and older generations of Xi manufactured before February 2011. Not valid from Xi Platinum Plus.

I get too low readings with my RaySafe Xi Light.

If the illuminance sensor is dirty, please clean it using a slightly dampened cloth. If the problem persists, contact Unfors Service Department.

I get strange readings when measuring HVL on mammography, in comparison to my manual HVL measurements.

Please make sure that the true thickness of your Al filters is accurately known and used in the calculation. A resolution in the order of 1 µm is needed for 0.1 mm thickness. Filters should be 0.999 purity.

"No detector found"

Is your detector plugged into the Xi Base with the mini USB cable? Try exchanging the short cable for the long cable (or vice versa) Your Xi may require service. Contact customer Service.

I want to measure kVp, but my RaySafe Xi only shows kV.

Certain x-ray generators (notably the GE AMX4+) have a low high voltage ripple frequency and a variable amplitude of the ripple. To get as accurate result as possible make sure the Xi detector get as much signal as possible. Many mobile x-ray systems have a fixed mA so it is not possible to increase dose rate by the settings. Place your Xi Detector closer to the collimator of the AMX4+ (or similar unit), and redo the exposure with the RF High detector choice.

Where do I place the Xi Detector to make a kV/dose/hvl measurement?

1. For general radiography, place the detector approximately 50 cm (~20") from the focal spot of the x-ray tube), perpendicular to the length of the tube. Using the light field, (10 cm x 10 cm) center the detector in the beam. Make certain the detector outlines are facing the x-ray beam.

2. For mammography, place the center of the MAM detector centered 6 cm ( 2 3/8") from the chest wall side. Make certain the detector cable is directed to the REAR, away from the chest wall side.

3. For CT kV, place the Xi detector in ISO-center on the table with the R/F-high sensor area aligned with the laser beam symbolizing the x-ray beam. Select a beam width that will cover the sensor area with a couple of mm on each side. Use a high mA >200 and select R/F-high on the Xi. Make exposure with the tube fixed in top position and without table movement.

How do I make a mAs measurement?

Your Xi must have mAs capability. A simple check is to look on the Right Side of your Xi for the mAs socket. Your Xi should be operating on its internal battery to make mAs measurements*. DO NOT USE THE WALL CHARGER*. Connect your Xi to the mAs socket of the x-ray generator with the supplied cable. Remove the jumper between the POS & NEG terminals on your generator. Turn your Xi ON. Make an exposure.

IMPORTANT NOTE: If recording data in XiView, your computer MUST be isolated from the AC power. Either use the Bluetooth wireless link (between the Xi and Computer) or use your laptop's internal battery if your Xi is wired to your laptop. Remove mAs cable and reconnect the jumper when completed.

Can I make a mAs, kV, HVL, and Dose measurement simultaneously?

Yes. Set your Xi RF detector in the x-ray beam, with your mAs cable attached. When the Xi RF detector is exposed, it will trigger mAs measurements.

My Xi CT probe doesn't measure kV

The CT probe is an ion chamber, intended for dose measurements only. It cannot measure kV.

My CT probe never Stabilizes

Turn your Xi base OFF. Set your CT probe on a level surface, and do not touch or move the CT probe. Turn your Xi base back ON. If the "Stabilizing" message does not disappear within 1-2 minutes, contact customer service. Your CT probe may need to be returned for service.

My CT probe dose readings are inaccurate.

Make certain ONLY the black ion chamber portion of the probe is exposed to radiation. Exposing the white base portion can result in wrong readings.

I get no readings on my Xi.

1. Make certain the Xi is turned ON.
2. Make certain the Auto Power Off time is adequate. Your Xi may be turning itself OFF.
3. Make certain your battery is charged. If Battery voltage is LOW, please plug in charger.
4. Make sure you have the proper detector selected. (Mam for mammo, RF for Radioscopic or fluoroscopic procedures).
5. Make certain your detector is plugged in (IS there a 'No detector connected' message?).
6. Make cerrtain your detector is facing the x-ray source
7. Make certain your collimator blades are OPEN.
8. Make certain your detector is positioned properly according to the quick guide.
9. If you are making a mA, mAs, or mAs/combo measurement, swap the polarity of your mA cables on the generator.
10. If you have made a mA or mAs measurement, make certain the mAs jumper is reconnected in the x-ray generator.
11. Make certain your x-ray unit under test is operational.
12. Move the Xi detector closer to the radiation source.

My kV readings are much higher than expected.

If using PMMA, Al or other added filtration in the beam please remove the added filtration. kV is best measured with no added filtration. For mammography see manual for how to measure best kV for each beam quality.

My Xi was upgraded to Platinum, and the AMX4+ selection is missing from the RF detector menu.

The latest version of Xi Platinum (5.x and above) automatically corrects for the AMX4+ waveform when calculating kVp.

When using my Bluetooth adapter I receive an error message in Xi View saying CRC error.

CRC error means that part of the data has been lost or altered in transit. This could happen if one operates the Bluetooth close to its maximum range, or if there is something interfering with the Bluetooth. Try moving the base unit closer to the computer.

When measuring on a Single Phase X-ray machine I am not able to get a kVp reading on my Xi.

On single phase units, One has to make sure to use RF High at a signal level well above 1mGy/s. Make sure the signal level is high enough to get a KVp reading instead of only kV by moving the Xi detector closer to the x-ray source.

Do I need to make any corrections or calculations with the dose reading to determine the actual CTDI of a multislice CT scanner when used in axial mode with a collimation of 40mm?

The only calculation needed is the normal calculation for CTDI. (CTDI = [measured value in mGy]*10/4[cm]). Correction for air pressure and temperature is automatically applied to the reading before display.

I receive a "detector comm. error" when using my Xi.

This could be caused by not having a long enough calc delay when making an exposure. If this does not solve your problem try using another cable.

What do the RaySafe Xi display codes mean?

Display Code: ***
Measurement has started

Display Code: - - -
No value can be calculated

Display Code: < 1 ms
Les than 1 ms valid samples

Display Code: LoSignal
The dose rate is too low to calculate a value (Increase mA or move closer to x-ray source)

Display Code: HiSignal
The dose rate is too high to calculate a value (Increase FDD or decrease mA)

Display Code: LoRange
Calculated kV is less than specified range

Display Code: HiRange
Calculated kV has exceeded specified range

Display Code: t < delay
The exposure time is not long enough to calculate a value. If applicable set trig delay to 0.

Display Code: Ofl.
Overflow, i.e. calculated value is numerically higher than can be displayed.

Display Code: Auto range out of order
At least one of the measuring ranges is out of order.

Display Code: Zero adjust out of range
Hardware offset levels may be out of range due to extreme temperatures.
This can happen if exposure is made during Zero adjust.

Display Code: Offset out of range
Ionization chamber current fails to reach a stable level when the RaySafe Xi CT Detector is turned on.

Display Code: Battery down
The battery must be charged before any measurements can be made.
It is enough to attach the power adapter and let it charge for a minute before trying again and measure with attached power adapter.

Display Code: Detector is incompatible
The version of the connected detector is not compatible with the RaySafe Xi Base Unit version.

My ThinX shows this screen, why?


  • If you just replaced the battery, this means that your ThinX is starting up. Be patient and wait for a while.
  • If the screen appears when you are exposing the ThinX to radiation, you need to replace the battery (model CR2450). Follow the instructions in the user manual: ThinX RAD or ThinX Intra. We recommend using a battery from GP Batteries.

I get an "Instrument error" instead of readings. What shall I do?


If the screen shows "Instrument error" followed by an error code, you shall always contact RaySafe Technical Support.

Note: If the error code is "SE:4, CE:0, OE:0", a firmware upgrade is needed. Follow the instructions in the Service Request Form.

Can I change the dose unit on my ThinX?

Yes. Irradiate your ThinX with a sequence of pulses: 3 short, 3 long, 3 short. (Short: <150 ms, long: >300 ms.) The sequence must be performed within 10 minutes. The message "Confirm unit change to Gy?" or "Confirm unit change to R?" is displayed. To confirm, make an exposure of any length within 20 seconds. The message "Unit changed!" is displayed and the ThinX will show values in the new unit. (1 Gy = 114.1 R)

How do I use the DXR+ on mammography machines?

The DXR+ works well placed on the examination table. Use as high kV as possible.

Note: Do not position the DXR+ on top of a magnification table, since the signal is too low there.

Can I replace the battery in the DXR+ myself?

No, you have to send it to RaySafe for battery replacement. Fill in a Service Request to get it done.

Can I use DXR+ for measuring a CT dose profile?

No. The DXR+ has to be irradiated from the printed X-ray arrow and with a continuous field to give a correct result.


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