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Kaidi KD-902 High Frequency Radar Level Meter/Transmitter Water Solid Tank Radar Level Meter

Kaidi KD-902 High Frequency Radar Level Meter/Transmitter Water Solid Tank Radar Level Meter
Temperature and pressure resistant, slightly corrosive liquids
Measuring Range:
Protection Grade:
Process Pressure:
Process Temperature:
-40~130℃(standard type)/-40~250℃(high temperature type)
Process Connection:
Threads, flanges
Explosion proof certification:
Exia ⅡC T6 Ga / Exd IIC T6 Gb
Outer Covering:
Aluminum Single Chamber / Aluminum Double Chamber / Plastic / Stainless Steel Single Chamber
Power supply
Two-wire system (DC24V) Four-wire system (DC24V/AC220V)
Signal output
(4 ~ 20) mA/HART (2-wire /4-wire) RS485/ Modbus
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1.  Product  Overview

High Frequency Radar Level Meter 902 adopted 26G high frequency radar sensor, the maximum measurement range can reach up to 30 meters. Antenna is optimized further processing, the new fast microprocessors have higher speed and efficiency can be done signal analysis, the instrumentation can be used for reactor, solid silo and very complex measurement environment.



Radar level transmitter antenna microwave pulse is narrow, the downward transmission antenna. Microwave exposure to the medium surface is reflected back again by the antenna system receives, sends the signal to the electronic circuit automatically converted into level signals (because the microwave propagation speed, electromagnetic wave to reach the target and the reflected back to the receiver this time is almost instantaneous).

      A    Range set

      B    Low adjustment

      C    High

      D    Blind area 

Datum measurement:  Screw thread bottom or the sealing surface of the flange.

Note: Make sure the radar level meter the highest level cannot enter the measuring blind area (Figure D shown below).

  •  The characteristics of 26G radar level meter:

Ø Small antenna size, easy to install; Non-contact radar, no wear, no pollution.

Ø Shorter wavelength, and there is better reflection on the solid surface.

Ø The measurement blind zone is smaller, and good results can be obtained for the measurement of small tanks.

Ø Hardly affected by corrosion and slight foam.

Ø Hardly affected by water vapor, temperature and pressure changes.

Ø Severe dust environment will not affect electromagnetic wave work.

Ø High signal-to-noise ratio, better performance can be obtained even with fluctuations.

Ø The wave speed gathering effect is very good, with various types of antennas, it can meet 90% of the working conditions.

2. Product  Introduction 


Application:Temperature and pressure resistant liquid,Slightly corrosive liquid

Measuring Range:0~30 meters

Process Connection:Thread, Flange

Process  Temperature:-40℃~130℃(Standard type)

-40℃~230℃(High temperature type)  

Process Pressure:-0.1~4.0MPa

Accuracy: ±5mm   

Protection Grade:IP67   

Frequency Range: 26GHz 

Supply:2-wire(DC24V)/ 4-wire(DC24V /AC220V)

Display: Four-digit LCD programmable

Signal Output:4... 20mA /HART(2-wire / 4-wire)


Outer Covering:Aluminum / Plastic / Stainless steel

Explosion-proof Grade:ExiaⅡC T6 Ga/ Exd ⅡC T6 Gb 

3. The  Installation Requirements

 Installation notes:

There should be no obstacles between the bottom of the antenna and the surface of the measured medium, and the installation in the tank should be avoided as much as possible, such as: human ladders, limit switches, heating equipment, brackets, etc. Also note that the microwave beam must not intersect the material flow.

When installing, pay attention to the maximum liquid level not to enter the blind area of the measurement; the instrument must be kept a certain distance from the tank wall; the installation of the instrument should make the antenna emission direction perpendicular to the surface of the measured medium as much as possible.

Instruments installed in explosion-proof areas must comply with the national installation regulations for explosion-proof hazardous areas. Explosion-proof instruments can be installed in places with explosion-proof requirements, and the instruments must be connected to the ground. The shell of the explosion-proof instrument is made of cast aluminum.

Installation location:

  • The instrument is installed at 1/4 or 1/6 of the diameter of the tank.  

          Note: The minimum distance from the tank wall should be 200mm.

                                                                                                          ① datum           ②The container center or axis of symmetry


  • For conical tanks, the top is flat, and the meter needs to be installed in the middle of the tank top. It can be guaranteed to measure to the bottom of the cone.


  • l Container takeover requirements: 

    Make sure that the antenna extends into the tank at least 10mm away.

  • Typical installation errors

Ø Conical tank

The instrument cannot be installed above the inlet. 

Note: Sun-shading and rain-proof measures should be taken during outdoor installation..              

                                                                                                                               ①Correct  ②Error  rainproof measures


Ø The meter cannot be installed in the middle of the top of an arched or round tank. In addition to producing indirect echoes, it will also be affected by multiple echoes. Multiple echoes may be larger than the signal threshold of true echoes, because multiple echoes can be concentrated through the top, so they cannot be installed in the center.  

                                                                                                                                                ①Correct  ②Error


Ø When there are obstacles in the tank that affect the measurement, it is necessary to install a reflector to measure normally.

                                                                                                                                                         ①Correct  ②Error

Measurement with stirring:

When there is stirring in the measuring tank, please try to stay away from the stirring paddle. After the instrument is installed, it is necessary to perform "false echo learning" in the stirring state to eliminate the influence of false echoes generated by the stirring blade. If foam or waves are generated during the stirring process, the still-pipe installation method should be used.

Installation of guided wave tube:

Ø The instrument is equipped with guide wave tube (or bypass tube) for measurement, which can avoid the influence of obstacles and foam in the container on the measurement.

Ø Due to stirring or some process reactions, foam will be formed on the surface of the liquid, and the foam will attenuate the signal, so a stilling wave tube should be installed for measurement.

Ø Install guide wave tube during measurement, the minimum diameter of guide wave tube should be 50mm. When connecting still pipes, avoid large cracks and welds. If necessary, "false echo learning" is required.

Ø When measuring with adhesive medium, the guided wave tube should not be used.


4. The Electrical Connection  

  • The power supply voltage:

(4~20)mA/HART (Two wire system)

 The power supply and the output current signal sharing a two core shield cable. The supply voltage range see technical data. For intrinsically safe type must be a safety barrier between the power supply and the instrument.

(4~20)mA/HART(Four wire system)

Separate power supply and the current signal, respectively using a two-core shielded cable. The supply voltage range see technical data.

RS485 / Modbus 

Power supply and Modbus signal line separated respectively using a two-core shielded cable, the power supply voltage range see technical data.

  • Cable Connection

General Introduction

Supply cable can use ordinary two-core cable,  the cable diameter should be (6~12) mm, to ensure that the cable entry seal. If electromagnetic interference exists, recommended to use shielded cable.

 (4~20) mA /HART(Two-wire)

Supply cable can use ordinary two-core cable.

 (4~20) mA /HART(Four-wire)

Supply cable should be used with a dedicated ground cable


 Shielded cable should be used for the power supply cable.

Shielding and wiring

Both ends of the shielded cable should be grounded. Inside the sensor, the shield must be connected to the internal ground terminal. The external ground terminal on the enclosure must be connected to the ground.

If there is ground current, the shielded cable must be grounded through a ceramic capacitor (for example: 1nF/1500V) far away from the shielding end of the instrument side to block direct and bypass high-frequency interference signals.

  • Connection  mode

Ø  24V  two wire wiring diagram as follows:

 Ø  6~24V Modbus-RS485 wiring diagram as follows:

  • Explosion Proof Connection

The explosion-proof form of this product is intrinsically safe.The intrinsic safety version sensors (Exia Ⅱc T6) use Alu-die casting housing and filling Silicone rubber sealants internal structure aimed to prevent sparks resulted from circuit failure from leaking out. It is applicable for the continuous level measurement of flammable medium under Exia Ⅱc T6.

A safety barrier FBS-2 must be used together with the intrinsic safety instrument. It is an associated device to this product for the power supply of this product. The main specification is intrinsic safety: ExiaⅡc, voltage of power supply: 24V DC±5%, short-circuit current: 135mA, operating current: 4...20mA.

All cables must be shielded. The max length is 500m for the cable from the barrier to the sensor. Stray capacitor≤0.1μF/Km, stray inductance 1mH/Km. Instrument must be connected to the ground potential. Any unapproved associated device is not allowed to be used.


 Safety  instructions:

Ø Please observe the local electrical code requirements!

Ø Please comply with local requirements for personnel health and safety regulations.

    All electrical components of instrument operation must be completed by the formal training of professionals.

Ø Please check the instrument nameplate to provide product specifications meet your requirements. Please make sure that the power supply voltage and instrument nameplate on the requirements.

 Protection  grade:

This meter fully meets the requirements of protection class IP66/IP67, please ensure the waterproof characteristics of the cable seal.  As shown below:

     How to install to meet the requirements of IP67:

     Please make sure that the sealing head is not damaged.

     Please make sure that the cable is not damaged.

     Please make sure that the cable for use with electrical connection specification.

     Cable into the electrical interface before its curved downward, ensure that the water will not flow into the shell, see the①

     Tighten the cable seal head, see the②

     Please electrical interface will not use blind plug tight, see the③




5. Instrument Commissioning

Three kinds of debugging method:

1) Display / Button (With split display, you need to debug on the split)  

2) Debug through computer software   

3) HART Handheld programmer


Display / Button: 

Debug the meter through the 4 buttons on the display screen. The debugging menu has four languages to choose from. The measured value can be read very clearly through the glass window.

Display / Button    

                                                                                                                  ① Liquid crystal display(LCD)   ② Adjust by button


 PC debugging:

Connected to PC by HART

① USB interface      ②  Radar level meter    ③ HART converter    ④  250Ω resistor



 HART  handheld  programmer:

① HART handheld programmer    ②  Radar level meter    ③  250 Ω Resistor


6. Structure Size   (Unit: mm)

The outer shell

Ø Cast aluminum shell

Plastic shell


Appearance  size:


 Flange  type:

7. Technical Parameters

General data

Process Connection 

Thread G1½″A / Thread 1½″NPT /  Flange

Antenna Material

Stainless steel

The outer shell material 

Cast aluminum, stainless steel, plastic 

The seal between the shell and cover

Silicone rubber

Casing window


The ground terminal 

 Stainless steel

The power supply voltage

Two wire system

24V DC

Four wire system

6~24V DC   ( Modbus-RS485 )

198 ~242 VAC  (Flameproof type /Double chamber)

110 VAC (Flameproof type /Double chamber)

Power dissipation

Max. 22.5mA / 1W

Allowable ripple

- <100Hz                                   Uss<lV

- (100~100K) Hz                      Uss<l0mV

The cable parameters

Cable entrance / plug

1  M20xl.5 cable entrance

 1  Blind plug (M20×l.5)


 The maximum usable wire is 2.5mm²

Output parameters

The output signal

(4 ~ 20) mA / Modbus-RS485



Fault signal

Constant current output; 20. 5mA;22mA;3.9mA

The integral time 

(0 ~ 36) s, adjustable

Two-wire load resistance

See below

Four-wire load resistance

 Max 500Ω

The integral time

 (0 ~ 36) s, adjustable

Characteristic Parameters
Blind area

the ends of the antenna

Maximum distance measuremen

30 meters

Microwave frequency


Communication interface 

HART communication protocol

Modbus-RS485 communication protoco

The measurement interval

about 1 second (depending on the parameter settings)

Adjust the time

about 1 second (depending on the parameter settings)

Display resolution

1 mm

Working storage and transportation temperature


Process temperature (the temperature of the antenna part)

 (-40~130)℃ Standard type/ (-40~230)℃  High temperature type

Relative humidit

˂ 95%



Shock resistance

Vibration frequency (10~150) Hz,

maximum vibration acceleration l0m/s²

8.   Meter  Linearity


The launch angle depends on the antenna size

-¢46mm                         18°

-¢76mm                         12°

-¢96mm                          8°

-¢121mm                        6°

Accuracy                         See below(±5mm)

9. Product  Model  Selection



P    Standard (Non-explosion-proof)

I     Intrinsically safe (Exia C T6 Ga)

D    Flameproof (Exd C T6 Gb)

Process Connection Material

                      G   Thread G1½A / Stainless Steel 304

                      N   Thread 1½″ NPT / Stainless Steel 304

                      Y    Special Custom

Flange selection (specification / code / material)


Stainless steel 304

Stainless steel 316L











Antenna Type / Material

A   Horn Antenna Φ46mm / Stainless Steel 316L

B   Horn Antenna Φ76mm / Stainless Steel 316L

C   Horn Antenna Φ96mm / Stainless Steel 316L

Y   Special Custom

                                             Seal Up / Process Temperature

V   Viton / (-40~130

K   Kalrez / (-40~230) 

The  Electronic Unit

3    (4~20) mA / 24V DC / HART 2-wire system

   (4~20) mA / 220V AC / HART 4-wire system

5    Modbus-RS485  / 6~24V / 4-wire system

Outer Covering / Protection  Grade

   Aluminum / Single chamber / IP67

H    Aluminum / Double chamber / IP67

G   Plastic / Single chamber / IP65

K   Stainless steel / Single chamber / IP67

Cable Line

M    M 20×1.5

N    ½ NPT

Field Display /The Programmer

A    With

X    Without

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