FAQs on RetroSign GRX

What is the difference between RetroSign GRX-1, GRX-3 and GRX-7?

The only difference between the 3 models is the number of observation angles measured. RetroSign GRX-1 measures one main observation angle, RetroSign GRX-3 measures three observation angles and RetroSign GRX-7 measures seven observation angles. The actual observation angle(s) measured depend on the geometry required by the specific standard and is controlled by the angle adapter.

Can a RetroSign GRX-1 be upgraded to a RetroSign GRX-3 or a GRX-7?

Yes it can as each RetroSign GRX contains all available features. The upgrade can be ordered from DELTA and can be done easily by the user by scanning a QR code forwarded by e-mail by DELTA.

Can a RetroSign GRX be upgrade with additional features?

Yes it can as each RetroSign GRX contains all available features. The upgrade can be ordered from DELTA and can be done easily by the user by scanning a QR code forwarded by e-mail by DELTA.

Can my RetroSign measure both ASTM (US) and CEN (European) geometry?

Yes it can. You just need to purchase a second basic angle adapter to cover the other geometry. Each angle adapter will have its own calibration unit at the back of the adapter which has to be used for calibrating the GRX for this particular geometry.

Can my RetroSign also measure retroreflection of High Visibility Clothing, License plates and Conspicuity Tapes?

Yes it can. Check our price list for an overview on angle adapter solutions available or contact DELTA for assistance.

How long time does it take to measure a road sign?

To make one retroreflection measurement takes 1 second independent of the number of observation angles measured.

What is the benefit of measuring three or seven observation angles?

The main observation angle (as measured by RetroSign GRX-1) mainly show the retroreflection as observed by the driver in a passenger car. The additional observation angles offered by RetroSign GRX-3 and GRX-7 shows the retroreflection is seen by a driver in larger vehicles like SUVs, lorries and busses. .

What is the benefit of using Point Aperture Geometry over Annular Aperture Geometry?

Point Aperture Geometry ensures accurate readings that replicate real-world driving conditions and correspond to laboratory readings. Point Aperture Geometry also enables the user to determine whether a microprismatic sign sheeting material has been applied correctly. See: Technical note RS106

Does the sun affect the measurement result?

No, RetroSign has a built-in Stray Light Compensation effectively ensuring that ambient light from the sun or other light sources does not affect the accuracy of the measurement.


How fast does the battery charge?

The battery is fully charged within 45 min.

How many measurements can I take with a fully charged battery?

Depends on how the instrument is used; the use of LCD backlight, sound, GPS, RFID, Bluetooth and the measurements schedule all effects the number of measurements possible. A fully charged and fresh battery should be able to make around 800 measurements.

When do we know that the battery should be replaced?

A fresh battery will normally take at least 800 readings. If the number of measurement after recharging falls low it is time to replace.

How long does a battery last before it need to be replaced?

This depends on the use pattern as mentioned above. Do not recharge every time you use the instrument. It is better for the battery to discharge between charge cycles maximizing the battery life time, which is normally several years.

Can I change the battery myself?

Yes you can. Make sure the instrument is turned off, push on the side of the GRX housing where the battery is located and pull the battery out. Please see the attached instruction for details: RetroSign GRX, Battery.

Click here


Can I calibrate the RetroSign GRX myself?

Yes you can by using the calibration unit located at the back of the angle adapter. Please see the attached instruction for details: RetroSign GRX, Calibration.

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How often does the calibration standard need to be re-calibrated?

If kept dry in storage and taken well care of when used (no dirt, no scratches on the calibration normal surface) it can last several years without needing re-calibration. DELTA, however, recommends to have a re-calibration or replacement of calibration block done at least every two years to make sure that the calibration of the instruments is correct.

Is there an alternative to sending the calibration unit for re-calibration?

Yes, you can decide to purchase a new calibration unit from DELTA for your instrument, see our price list for details.

How do I know that the calibration block needs re-calibration or needs to be changed?

When the calibration block is scratched, dirty (and cannot be properly cleaned) or otherwise damaged, it is time to replace it.

Does the retroreflectometer itself need to be re-calibrated?

The instrument comes calibrated from the factory. Unless the instrument has been damaged after e.g. being dropped or run over by a vehicle the instrument itself does not need re-calibration.

Using the features

How do I mount and operate the Extension Pole?

Please see the attached instruction for use details: RetroSign GRX, Extension Pole.

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Instrument service

How often does the RetroSign GRX need to be serviced?

RetroSign is a very robust instrument which can stand daily use without need for service. If you should have an accident with the instruments (being dropped, being hit hard and alike) DELTA recommends servicing the instrument. If you want to be sure the instruments work correctly at all times you may consider an instrument service at DELTA at regular intervals. If the instrument is used every day DELTA recommend these intervals being once a year, if used less often a service every 2-3 years will do.

How do I know if/when the instrument need service?

If the instrument doesn’t work at all, if the instrument status inform that it has detected problems (constant errors and/or warnings) or the measurement are obviously wrong the instrument need urgent service.

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