• Radiation Alert® Sentry EC Operation Manual

    The Radiation Alert® Sentry EC and Sentry Operation Manual.


The Sentry & Sentry EC / Online Operation Manual

How To Use This Manual

Simply click on the "+" or "-" buttons to the left of the chapter titles below to expand that chapter. If you would like to view our video operation manual, click here.

Chapter 1: Introduction

The Sentry is a Personal Alarming Dosimeter and Rate Meter that measures gamma and x-ray radiation and provides dose rate monitoring in a small rugged package. The Sentry works as a stand alone unit or in conjuction with the optional SentryCom Software, which can assist in tracking exposure to generate incident reconstruction and analysis.The Sentry employs two bright pulsating LEDs, an Audio Alert, and/or a Vibration Alert for the selectable alert levels. Default Dose Alarm is 500 mR and the Default Rate Alarm is 50 mR/hr. If ordered in the optional μSv, the default Dose Alarm is 5000 μSv and the Default Rate Alarm is 500 μSv/hr. Coupled with the software, The Sentry can provide dose measurement, dose rate measurement, and dose history. It also enables you to easily set the alert to your desired levels for dose and rate.

Chapter 2: User Interface


There are two LEDs labeled Dose and Rate located on the endpanel. The LED labeled Dose will light when the Dose warning or alert is going off. The LED labeled Rate will light when the Rate warning or alert is going off.



The Sentry has two switches on the top of the unit. The first, located near the center of the end panel controls the power (ON/OFF), vibration alarm (VIBE), or the the audio and vibrate alarm (AUDIO). The second switch, located on the right of the unit, controls the audio clicks that sound with every count. It has two icons labeling the positions. Clicks on. Clicks off.

This switch is also used to turn off active alerts and warnings.


The Sentry vs. The Sentry EC

The Sentry has a serial header located in the battery compartment (see “Connecting The Sentry to a PC”), a headphone jack, non-compensated GM tube, and the enclosure is made of impact resistant ABS Plastic. The Sentry EC has a mini-USB port located on the end panel of the instrument, no headphone jack, an energy compensated GM tube, and an aluminum enclosure.

Chapter 3: Alert Modes

When The Sentry is initially switched on, the Sentry will conduct an alarm test. You will hear one high to low alert and feel a vibration. The audio and vibrating alert has two stages; The Warning Alert and The Alarm.


Audio and Vibrate Mode

The Warning Alert The first stage of the alert is triggered when you reach the set warning level. The warning audio alert pulsates from high to low with a 1 second delay accompanied by a pulsating vibration. The flashing LED indicates a Rate or Dose Warning. The Alarm The second stage of the alert is triggered when you have reached the set alarm threshold. The full alarm is a pulsating beeping sound with no pause accompanied by a pulsating vibration. The solidly lit LED indicates a Rate or Dose Alarm or both.


Vibrate Mode

The Warning Alert The first stage of the alert is triggered when you reach the set warning level. The warning vibration and the flashing LED indicates a warning. A flashing LED indicates a Rate or Dose Warning.


The Alarm

The second stage of the alert is triggered when you have reached the set alarm threshold. The full alert is a pulsating vibration notably faster than the warning. The solidly lit LED indicates a Rate or Dose Alarm or both.


Acknowledging an Alert

To turn off the alert, change the position of the audio clicks switch. This will tell the unit that you have ackowledged the alert. You can switch it back if you want clicks or no clicks and the alert will remain off. After leaving the field detected, the alert resets itself and will reset to alert the next time you enter a field corresponding to the preset alert and warning levels. If the unit is set to the Audio and Vibrate Alert mode, users can turn off the audio portion of the alert by switching the mode switch to “vibe”. The vibration alert and the LED will continue without the audio alert.

Chapter 4: The SentryCom Software

The SentryCom Software enables the users to change the alert levels for both dose and rate, set the time and date, as well as download incident data.


Connecting The Sentry to a PC

To connect the Sentry to a PC, open the battery door, and move the 9-volt battery out of the way to locate the 4 pin header. Attach the provided cable as shown to the header connector and the other end to your computer’s serial port. A USB Serial adapter can be used if your computer does not have a serial port. Turn on The Sentry.

Launch The SentryCom Software, select the Com Port number assigned to your Sentry, and click “Retrieve Current Settings”. This will populate the fields with the current alert and time/date settings, as well as the calibration factor.

For help identifying the COM Port Number associated with your Sentry, go to The Device Manager on your PC. See Fig. 6 for information on accessing the Device Manager.


Changing your Default Alert Levels

When you open The SentryCom Software, the “Settings” tab opens by default. To change the alert levels on The Sentry, click on the field containing the setting you would like to change. After you have changed them to your desired settings, click “Update with New Settings” to update The Sentry. You will hear a beep after the settings are stored in The Sentry. Note: The minimum warning value for both is 0.1. To turn off the warning alerts, enter “0” (Zero) “0” = “OFF” .


Changing from mR & mR/hr to μSv & μSv/hr

WARNING: When changing the units from mR & mR/ hr to μSv & μSv/hr, ALL THE ACCUMULATED DOSE DATA STORED IN THE SENTRY WILL BE ERASED. To change the units of measurement, click the desired
unit and click the “Update with New Settings” button.


Data Logging Frequency

This setting will determine how often data is recorded. For example, if you set the frequency to 1 minute, there will be a record every 1 minute when you download your accumulated data from The Sentry. (See Fig. 8)


Changing the Time and Date on The Sentry

To display the current date and time setting for The Sentry, click “Get Date and Time”. To set the date and time of The Sentry to the current date and time of your PC, click “Set Date and Time to PC” and then click “Update with New Settings” button. (See Fig. 3)


Calibration Factor

If the factory defaults of The Sentry do not meet your needs, you can adjust the deadtime and the cal factor by inputting your new settings in the Calibration tab.


Retrieving Accumulated Dose Data

The Sentry allows the user to download and log data that has been accumulated in The Sentry’s memory. To download your data, connect your computer to The Sentry as described in Connecting The Sentry to the PC. Click on the “Data Log” tab, then click “Retrieve Data”. After the table in the Data Log tab has been
populated, you can click “Save Data” to save it to your computer as a text file. Accumulated Exposure readings labeled “Power On” indicate that the unit was turned off and on.

Chapter 5: Changing the Batteries on The Sentry EC

WARNING: When changing the battery, please be aware that there is high voltage on the board inside the unit. Improper handling could cause injury. Aside from the batteries, there are no user serviceable parts in the Sentry.


9-Volt Battery

To change the 9-volt battery, first make sure that the USB cap is inserted into the jack on the top of the unit. This will help hold the circuit board in place when changing the 9-volt battery. Next, unscrew the bottom endpanel (the endpanel with the serial number), and remove it. Unsnap the battery and replace it with a new one. Put the battery back in place and screw the endpanel back on to the unit.


Button Battery (CR-1025)

The typical battery life is 75,000 hours. If you are getting errant time and date stamps on your accumulated dose data, the button battery



1. Remove 9 volt battery
2. Remove 2 screws holding enclosure together
3. Turn the Sentry over so the label is facing you.
4. Using your thumbnail, hold the center switch while separating the enclosure halves.You want to ensure you do not pull the end panel
out of place. The speaker and Vibe are mounted to the top half of the case and you do not want to pull the wires out of the circuit board.
5. Once the enclosure is separated, you can replace the coin battery.
6. To reassemble, tuck the wires back inside the unit and carefully replace the top half. Replace the 2 screws and battery.
7. You will have to reset the Time and Date.


Sentry EC:

1. Unplug the USB cap from the mini-USB port on the top of the unit.
2. Unscrew the bottom endpanel (the endpanel with the serial number), and remove it.
3. Disconnect the 9-volt battery from the unit to prevent any shock or damage to the board.
4. Gently pull the circuit board out of the bottom of the unit with the belt clip side facing up (fig. 10).
5. Replace the small button battery located next to the transformer.
6. After replacing the battery, slide the circuit board back into the case, plug in the USB cap to hold the board in place.
7. Replace the 9-volt battery, and screw the endpanel back on to the unit.

Appendix A: Troubleshooting

When I download the accumulated dose data, the time and date read in strange characters like “3F:7F:7F”.


The button battery in the unit needs to be changed.


I’ve tried a variety of different COM ports when connecting to unit using the Sentry Com Software, but it does not connect.


Ensure that the device is turned on.


Open the “Device Manager” and go to “Ports” to see what the com port number is for that unit. If you have the correct port number and it still doesn’t connect, make sure that the cable is properly connected to both the unit and the computer.


When I turn on the unit, I get a “chirping sound” that isn’t like the beeps I get for each count.


The chirps are to notify the user of two possible situations. First, check that the 9-volt battery is good. When the voltage on the battery gets too low, the chirping starts to let the user know that the battery needs to be changed. The other is to let the user know that the unit is not recieving counts and that the GM tube or the unit itself has been damaged. If you change the battery and are still hearing the chirps after 5 minutes of the unit being on, please contact S.E. International, Inc. for assistance.


In the event that you stored The Sentry without a 9-volt battery or with a depleated one, the date on the unit will revert to 1/1/00. If you are not using the software to track your data, this is not an issue. If you are using The SentryCom Software, simply connect the unit to a PC, and reset the time and date before use.


Appendix B: Specifications


Sentry EC Radiation Dosimeter and Ratemeter

The Radiation Alert® Sentry EC is a Personal Alarming Dosimeter / Ratemeter designed to ensure the safety of personnel that work in occupations with potential x-ray or gamma exposure.

The pocket sized unit has an energy compensated tube for a linear response to gamma and built in memory for recording data points for tracking accumulated exposure. The SentryCom Software option enables you to generate incident reconstruction for analysis. The software also permits you to easily set the vibrating and audio alert to your desired levels for dose (>1.0 mR/10 µSv) and dose rate (>1.0 mR/hr/10 µSv/hr).

Use the audio switch to choose between audible clicks with each count recieved or a discreet silent mode.


Energy Compensated GM Tube

Dose Rate Linearity

Better than ±15% up to 15 R

Energy Response

Down to 20 KeV


Typically ±15% of reading (Cs137)

Gamma Sensitivity

1.5 cps/mR/hr (Co60)

Operating Range

Dose Rate: 0.1 mR/hr - 15 R/hr (1 µSv/hr - .15 Sv/hr)
Accumulated Dose: 0.1 mR - 65 R (1 µSv - .65 Sv)

Gamma SensitivityAudible Alarms

Accumulated Dose & Dose Rate, 90db @ 1 ft.

Alarm Thresholds

Default: Dose 500 mR / Rate 50 mR/hr
Sievert Option: Dose 5000 μSv / Rate 500 μSv/hr Alarm and warning levels are user selectable with the optional SentryCom Software.

Switch Functions

Power, Vibrate & Audible Alert, Silent Vibrating Only Alert, and Audio Clicks On/Off.

Power Requirements

9-Volt Alkaline Battery Approx. 1500 hrs at normal background.


Alodized Aluminum Housing w/ Metal Belt Clip

Energy ResponseOutputs


Temperature Range

-20° - + 50°C (-4° - +122°F)


243 g (8.6 oz)


106 x 67 x 28 mm (4.2 X 2.7 X 1.1 in)

Limited Warranty

1 year limited

Appendix: WARRANTY

WARRANTOR: S.E. International, Inc., P.O. Box 39, 436 Farm Road, Summertown, TN 38483-0039, USA, 931.964.3561 ELEMENTS OF WARRANTY: S.E. International, Inc., warrants for 1 year the Geiger-Mueller tube and for one year all materials and craftsmanship in this product to be free from all defects with only the limitations set out below.

WARRANTY DURATION: The warranty shall terminate and be of no further effect one year after the original date of purchase of the product or at the time the product is: a) damaged or not maintained as is reasonable or necessary, b) modified, c) repaired by someone other than the warrantor for a defect or malfunction covered by this Warranty, d) contaminated with radioactive materials, or e) used in a manner or purpose for which the instrument was not intended or contrary to S.E. International, Inc.’s written instructions. This warranty does not apply to any product subjected to corrosive elements, misuse, abuse, or neglect.

STATEMENT OF REMEDY: In the event that the product does not conform to the warranty at any time while this warranty is effective, the Warrantor will repair the defect and return the instrument to you prepaid, without charge for parts or labor. NOTE: While the product will be remedied under this warranty without charge, this warranty does not cover or provide for the reimbursement or payment of incidental or consequential damages arising from the use of or the inability to use this product. The liability of the company arising out of the supplying of this instrument, or its use, whether on warranties or otherwise, shall not in any case exceed the cost of correcting defects in the instrument, and after the said one year period all such liability shall terminate. Any implied warranty is limited to the duration of the written warranty.

PROCEDURE FOR OBTAINING PERFORMANCE OF WARRANTY: In the event that the product does not conform to this warranty, please write or call to the address above. S.E. International, Inc. will not accept contaminated instruments for calibration or repair under warranty or otherwise.

NOTE: Before using this instrument, the user must determine the suitability of the product for his or her intended use. The user assumes all risk and liability connected with such use.