DT-824S Portable Non-linear Junction Detector

Important Safety Instructions

The device will emit electromagnetic waves when working; please do not put the detection surface close to the human body for a long time.
The input voltage range of the adapter is 100V~240V. Voltages outside this range will damage the charger.
This device is a precision instrument and should not be disassembled by the user. Operations should only be performed by qualified service personnel. Do not drop the device or subject it to physical impact. Ensure cables are securely connected and avoid excessive tension.
To ensure safety, do not place the device or its backup battery in fire or water, as this may result in overheating, fire, short circuit, or explosion.
Do not place the device in environments with temperatures exceeding 70°C, such as a car in direct sunlight, as high temperatures may cause malfunction.
When not in use, the device should be kept indoors, out of direct sunlight. Avoid storage in dark rooms, laboratories, or places with corrosive chemicals.
Do not touch the electronic contacts of the device with fingers to prevent corrosion, which may cause malfunction.
Do not allow conductive foreign objects to touch the charging connector or interface, as this may cause a short circuit, fire, or electric shock.
Use only the original charger and charging cable for safe use of the device and battery.
Store the device in a dry and cool environment (10°C~25°C, humidity below 65%), free from dust and corrosive gases.
If the device is unused for 6 months or more, charge and discharge the battery every 3 months to maintain its chemical activity and prevent damage from long-term disuse.
Do not allow solvents such as alcohol, benzene, or thinner to contact the detector. Do not use a wet cloth or solvent for cleaning, as this may bend or crack the housing, leading to electric shock, malfunction, or fire.
In areas with multiple detectors operating simultaneously at the same transmitting frequency, frequency interference may occur. Adjust the transmitting frequency in a staggered manner to avoid misjudgment.
If the device has not been used for a long time or before important detection activities, have it tested by the dealer or yourself to ensure proper working condition.

Overview

The Portable Non-linear Junction Detector (NLJD) DT-824S is used for detecting explosive devices, eavesdropping equipment, and other suspicious electronic products. It operates by actively emitting a fundamental signal to an object under test and analyzing the returned second and third harmonic signals to identify the presence of non-linear junctions, indicative of electronic components.

Parameters

Function	Details
Detects and Identifies	Semiconductor junctions and corroded metal junctions.
Detection Capability	Can detect electronic devices containing semiconductor components in both working and non-working conditions.
Alarm	Provides audible and visual alarms when detecting electronic devices with semiconductor components or corroded metal junctions.
Operator Interface	Integrates harmonic intensity mode, peak harmonic time domain mode, and harmonic audio functions.
Harmonic Intensity Interface	Displays transmitted signal strength, second harmonic intensity, third harmonic intensity, and provides identification results: "semiconductor junction", "metal corrosion junction". Issues sound and light alarms.
Harmonic Time Domain Curve Interface	Shows the second and third harmonic intensity over time. The curve display time width can be set to 5, 10, 20, 30, or 60 seconds.
Harmonic Audio Output	Can play harmonic audio through headphones or speakers. Metal rust junctions and semiconductor junctions produce different characteristic sounds.
Low Voltage Alarm	Includes a low voltage alarm function, meeting GA 1236-2015 "Nonlinear Junction Detector" 5.2.2 requirements.

Weight of main unit (without battery)	≤ 0.5kg
Length of main unit	≤ 250mm
Power supply mode	Battery (non-replaceable)
Continuous working time	≥ 4 hours
Lower limit of working environment temperature	≥ -30°C
Upper limit of working ambient temperature	≤ 55°C
Lower limit of storage ambient temperature	≥ -40°C
Upper limit of storage ambient temperature	≤ 70°C
Humidity and heat of working environment	relative humidity 93% (40°C)
Protection class	≥ IP65
Semiconductor junction detection distance	Not less than 10,000 mm (GA1236-2015 Semiconductor Standard Test Sample)
Penetration ability	Not less than 550 mm brick wall (GA1236-2015 Semiconductor Standard Test Sample)
Alarm volume	≥ 60 dB

Unpacking

After opening the carrying case, verify that the case contains the following items:

Portable Non-linear Junction Detector x1
Adapter x1
Headphone x1
Test Sample x2 (labeled "Third Harmonic Test Tag" and "Second Harmonic Test Tag")

Component Names

The device is a handheld unit with a display screen at the top. Below the screen are several buttons and indicators. Labels point to: 'Display', 'Speaker', 'On/Off button', 'Detection surface' (on the top front), 'Mode switching/Return' button, 'Center button (Up, Down, Left, Right, Menu/Confirm)', 'Battery compartment' (rear), 'Charging indicator', 'Headphone jack', and 'Charging port' (bottom).

Center Button Functions

Button Icon	Function
⏻	On/Off button: Long press to turn on/off.
?	Mode switching button: Press to switch detection mode or return to the previous menu level.
✅	Menu/Confirmation button: Enter the main menu or confirm each operation.
⬆️	Menu direction "up" button: Increases the number of buttons.
⬇️	Menu direction "down" button: Decreases the numerical value.
⬅️	Menu direction "left" button: Adjusts volume down in the detection mode home interface.
➡️	Menu direction "right" button: Adjusts volume up in the detection mode home interface.

How to Use

Target Identification

When suspicious electronic equipment is detected (semiconductor junction), the second harmonic signal strength will be significantly stronger than the third harmonic signal strength.
When non-electronic equipment like metal oxides are detected (metal corrosion junctions), the third harmonic signal strength will be significantly stronger than the second harmonic signal strength.
The system provides auxiliary identification results displayed on the interface to help determine the target's nature. This is mainly for assistance; for complex environments, combine with practical experience for final identification.

Function Check

Remove the product from the carrying case.
Press and hold the "On/Off" button to turn on the detector. Plug in headphones if in a noisy environment.
The screen will display "POWER ON......".
Immediately enter the detection state after power on. Perform functional testing using the accessory semiconductor junction test body and metal corrosion junction test body. Direct the detection surface towards the test area and scan slowly and uniformly.
Check for obvious false alarms or distance attenuation for each test body.
If no abnormalities are found, normal operation can proceed. Contact the manufacturer if any significant abnormalities occur.

Detection Method

Take the device out of the carrying case, connect the headphone, and long press the "On/Off" button to power on the device.
When detecting, point the detection surface towards the object. Scan the target slowly and uniformly to ensure accuracy and minimize electromagnetic interference from simultaneous devices.
After detecting an electronic target, the device transmits the signal to the display and buzzer, identifying the target based on harmonic intensity and buzzer volume/audio. Auxiliary determination is provided. (Intersection or circle detection methods can be used for more accurate location).
Short press the "On/Off" button to bring up the shutdown confirmation window. Select "Action" to turn off the device and return it to the carrying case.

Mode Function Logic

The device offers different detection modes, each with configurable parameters.

Non-linear Junction Detection Mode

The 'Non-linear Junction Detection Mode' branches into settings for 'TX Power', 'TX Freq', 'DSP Gain', 'Alarm Setting', and 'Information'.

'TX Power' can be set to '30%(default)' or 'Auto-Adjust(ON/OFF)'.
'TX Freq' can be set to '2450MHz(default)' or 'Auto-Select(ON/OFF)'.
'DSP Gain' has options 'High/Medium/Low (default Medium)'.
'Alarm Setting' includes 'Volume' (High/Medium/Low, default Medium) and 'Alarm Threshold' (20%(default)).
'Information' leads to 'Device Information', 'Active', and 'Cancel' options, with 'Factory Reset' also accessible.

Time Domain Curve Detection Mode

The 'Time Domain Curve Detection Mode' includes 'Chart Setting', 'TX Power', 'TX Freq', 'DSP Gain', 'Alarm Setting', and 'Information'.

'Chart Setting' allows 'Graph Display(RX2/RX3)' and 'Time Interval(5s/10s/20s/30s/60s)'.
Other settings mirror those in the Non-linear Junction Detection Mode.

Harmonic Audio Detection Mode

The 'Harmonic Audio Detection Mode' includes 'Audio Setting', 'TX Power', 'TX Freq', 'DSP Gain', 'Alarm Setting', and 'Information'.

'Audio Setting' allows 'Graph Display RX2/RX3', 'Volume (High/Medium/Low, default Medium)', and 'Time Interval (5s/10s/20s/30s/60s)'.
Other settings mirror those in the Non-linear Junction Detection Mode.

Non-linear Junction Detection Mode

This is the default mode. The detector emits a high-frequency fundamental signal and analyzes the returned second and third harmonic signals to identify suspicious electronic products. The diagram shows signal strength meters (TX, RX2, RX3) and indicates 'Transmit power', 'Detection result', '3rd harmonic signal strength', and '2nd harmonic signal strength'. A 'SEMICOND' icon is associated with detection results.

Transmit power: Adjustable from 0% to 100% (default 30%), adjustable in 5% steps or continuously by long-pressing buttons.
Second-order signal strength: When this exceeds the threshold, the system identifies the object as a semiconductor junction, displayed on the left.
Third-order signal strength: When this exceeds the threshold, the system identifies the object as a metal corrosion junction, displayed on the left.

Device Icons and Indicators

Battery icon: Displays charge levels: 20%, 40%, 70%, 100%.
Volume icon: Represents volume levels: Volume 0 (?), Volume 1 (?), Volume 2, Volume 3 (?).
Detection icon: A magnifying glass with 'SEARCH......' indicates the device is transmitting a detection signal. A chip icon labeled 'SEMICOND' indicates a semiconductor junction is detected. A link icon labeled 'CORROSIVE' indicates a metal corrosion junction is detected.

TX Power

The 'Auto-Adjust' function turns on/off automatic transmit power adjustment.

ON: The device automatically selects transmit power based on the distance to the detected object (higher power for farther objects, lower for closer) for optimal detection results.
OFF: Transmit power is manually set and remains unchanged during detection.

Transmit power is adjustable from 0% to 100% (default 30%), in 5% steps or continuously. Quick setting is available via "up and down buttons" on the home interface.

Caution: When 'Auto-Adjust' is on, the manually set transmit power value becomes the highest threshold for automatic adjustment. For example, if manually set to 80%, the automatic adjustment range is 5%~80%.

TX Freq

'Auto-Select' allows the system to automatically select the transmit frequency.

ON: The device automatically selects the transmit frequency when the function is turned on. This selection occurs once each time the device is powered on.

Transmit frequency is adjustable manually from 2400~2500MHz (default 2450MHz), in 1MHz steps using "up and down buttons".

DSP Gain

The DSP gain is adjustable to High/Medium/Low (default medium):

High: Provides high gain for maximum detectable distance.
Medium: Provides medium gain for moderate detectable distance.
Low: Provides low gain for detection at close distances.

Alarm Setting

The alarm volume is adjustable in High/Medium/Low/Silent (default medium).

Alarm volume can be adjusted using "up and down buttons".
Quick Setting: Alarm volume can be set directly via "left and right buttons" on the detection mode home interface.

Alarm threshold is adjustable from 0% to 100% (default 20%). The alarm triggers when the set threshold for the second and third harmonics is reached. The threshold can be set using "up and down buttons" in 5% steps.

Information

The 'Information' menu displays device details and allows factory reset.

Device Information: Device name: Non-linear Junction Detector, SN No.: XXXXXXXXXXXXXX, Version: VXRXCX.

Clicking the "Factory Reset" button restores the system settings to their factory state.

Time Domain Curve Detection Mode

This mode displays the characteristics of second and third-order signal strengths over time, showing different curve patterns for various junction types.

Semiconductor junction: The second and third order signal strengths are stable, typically showing a smooth straight line on the time domain curve.
False junctions (e.g., metal corrosion): Signal strength is unstable, and the time domain curve appears as a jumping curve.
When a hard object taps the junction, oscillations intensify for false junctions, while real semiconductor junctions remain stable.

When detecting surfaces like walls or sofas, if a semiconductor junction is identified in the non-linear junction detection mode, switching to time domain curve mode can confirm stability. A smooth straight line indicates a semiconductor junction, while clear oscillation suggests a false junction like metal corrosion.

Chart Setting

Graph Display: Configurable for RX2/RX3.
Time Interval: Selectable from 5s, 10s, 20s, 30s, or 60s.

Harmonic Audio Detection Mode

This mode demodulates 2nd and 3rd order harmonic signatures to assist in detecting working electronic devices like hidden cameras or GPS units.

Semiconductor junction: Exhibits 2nd order harmonic signature audio (and sometimes 3rd order).
Working semiconductor junction: Presents current sound and low noise when listening via headphones, based on the second-order harmonic response.
False junctions (e.g., metal rust): Shows little response to the second-order harmonic audio; only the third-order harmonic characteristic audio is present.

If a semiconductor junction is detected in non-linear mode, switching to harmonic audio mode can help confirm. The presence of a second-order harmonic response with current sound and low noise indicates a working semiconductor junction. Only a third-order harmonic characteristic audio suggests a false junction like metal corrosion.

Audio Setting

Graph Display: Configurable for RX2/RX3.
Volume: Selectable from High/Medium/Low.
Time Interval: Selectable from 5s, 10s, 20s, 30s, or 60s.

Battery

Low Battery Alarm

When the battery level is 20% or less, the battery icon will show red (?). When the level drops below 10%, the device will automatically shut down.

Charging the Battery

Insert the Type-C end of the adapter into the device's charging port. The charging indicator lights up red when the power is on. An image shows a black wall adapter with a USB Type-C cable.

Battery Maintenance

This device is a sealed unit; the battery is non-replaceable by the user. Follow these principles for daily battery use:

Use only the original charger and charging cable for safe charging.
Store in a dry and cool environment (10°C~25°C, humidity below 65%), free from dust and corrosive gases.
If unused for 6 months or more, charge and discharge the battery every 3 months to maintain its chemical activity and prevent long-term damage.

Troubleshooting

The device cannot be turned on: Connect the power adapter to charge the device.
No sound from headphones:
- A. Incorrect or weak cable connection: Ensure the headphone cable is connected correctly and firmly.
- B. Headphone sound adjustment is too small: Adjust the output volume through the system menu.

Maintenance

To extend the device's service life, observe the following daily use precautions:

Pay attention to dust, moisture, and high temperatures.
Store the device indoors, away from direct sunlight, when not in use.
Ensure cable connections are firm and avoid excessive tension.
Avoid strong impacts and knocks during use.

Transportation

The device can be transported by rail, road, or sea. Secure it firmly during transport to prevent it from being upended, collapsed, or dropped.
The machine should be placed facing upwards and can be stacked up to 4 layers high.
Protect against dust, rain, moisture, and salt spray during transportation. Keep sharp objects away from the device.
Handle the device lightly during transportation and handling; avoid dropping or throwing.
For warranty service, keep the original packaging for transportation. Protect the detector from severe mechanical forces, as its components are sensitive to shocks and vibrations.
Inspect the device for shipping damage immediately upon delivery, note any damage on shipping documents, and notify the manufacturer.
Remove packaging carefully. Retain packaging if no specific recycling guidelines are provided.
Dispose of the device in an environmentally responsible manner, following appropriate disposal guidelines.