NKB-20RX Display Type AC current transmitter series

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Place of Origin:
Jiangsu, China (Mainland)
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Selling Units:
Single item
Single package size: 
10X10X10 cm
Single gross weight:
1.0 kg
Package Type:
in cartons for DC Current / Voltage Transducer
Lead Time :
Quantity(Unit) 1 - 1 >1
Est. Time(days) 30 To be negotiated


Measurement: AC Current measurement

 Four-bit 0.34 "digital tube display, range automatic conversion, decimal point automatically switch according to range

Isolation mode: power supply, input, output three-way complete isolation anti-jamming ability strong

Output: RS485 Communication Interface MODBUS-RTU protocol, etc.

Working principle: The internal use of microprocessor for mathematical operations, the nonlinear input signal can be extremely high precision linear correction. Lightweight, beautiful appearance, 35mm standard guide rail installation, easy loading and unloading


 The Display transmitter series is a kind of DC analog signal or digital signal device which changes the power and non-power parameters in the power grid into linear. It can be connected with a microcomputer through the RS485 serial interface to form a measurement and control system. The internal use of switching power supply, the auxiliary power supply requirements are low (power supply AC, DC General), the series has a strong anti-jamming performance, its anti-jamming performance in line with IEC electromagnetic compatibility level 3 provisions, other in line with GB/t 13978-92 provisions, the series is applicable to machinery, telecommunications, electricity, petroleum, chemical, steel , Sewage treatment, building construction, power plants, substations and other modern power supply and distribution systems, a high-performance intelligent transmitter.

Appearance dimensions

Technical parameters

Accuracy: ≤±0.2%R.O. or ±0.5%R.O.

Linearity: ≤±0.1%R.O.

Full scale calibration: ≤20%of R.O.

Input range: 0~5A, 0~1A

Output: RS485

0-point calibration: ≤10%of R.O.

Isolation strength: 1500Vdc (1 minutes) or AC Peak

Power supply, input, output three-side complete isolation

Working power supply: AC/DC24~265V±10 Power consumption: AC approx. 4VA,DC approx. 4W

Response time: ≤400msec.

Working environment: -10~60℃/less than 95% relative humidity (non-condensing state)

Storage environment: -20~70℃/less than 70% RH

Output ripple: ≤0.2%R.O. (Peak peak)

Output load: Voltage output maximum load capacity of 5 K;

Current output maximum load capacity of 510Ω

Shell material: ABS Fireproof Material

Mounting method: 35mm Standard guide rail or base screw mounting

Dimensions: (L) x55 (W) x75 (H) mm

Weight: approx. 400 g

Voltage and current parameter setting and key function

1, Alarm parameter settings: General Current/voltmeter users do not need to set data, press set greater than 3 seconds to enter the alarm mode settings menu, key shift, digital tube flashing, key modification, and then press set confirmation, down to continue to press set.

Press and hold the modifier key not to subtract, each click to modify the key to add.  

2, when displaying the measured value, press the modifier key to switch to the input, output display.

3, when the user for the current input, can be directly set through the menu display range.

4, in any set state, if there is no operation within 15 seconds, it is automatically returned to the measurement display.

5, special functions, this instrument can be used as DC voltage or AC voltmeter, do not need to change the terminal, as long as you want the voltage connected to the input, set to the parameters you want can be. This feat

Wiring diagram   Note: The wiring mode is based on the instrument brand wiring

MODBUS_RTU Communication Statute(This agreement adopts the master and answer method)


 NKB-20RX Intelligent Series Instrumentation/transmitter:


 NKB-20RX-27RX Intelligent Series of instrumentation/transmitters with a new design, revolutionized the concept of traditional meters, with multi-functional, high-precision, digital, programmable, compact structure, multi-screen display characteristics, it can meet the power industry in the future demand for meters.

 MODBUS Communication protocol:

ModBus Communication protocol allows NKB-20RX Intelligent series of instrumentation/transmitters with Schneider, Siemens, AB, GE and many other internationally renowned brands of programmable sequential controllers (PLC), RTU, SCADA systems, Information exchange and data transfer between DCS or monitoring systems that are ModBus compatible with third parties.

NKB-20RX Intelligent Series Instrumentation/transmitter simply add a set of monitoring software based on a computer (or industrial control machine) (e.g., Configuration King, Intouch, FIX, Synall, etc.) can form a set of power monitoring system.

Wide range of system integration:

Series instrumentation/transmitter provides a standard RS-485/422 communication interface and ModBus communication protocol, this communication protocol has been widely used by domestic and foreign power industry and industrial control industry as the standard of system integration.

Types and formats of communication data:

The information is transmitted asynchronously and in bytes. The communication information passed between the main station and the station is a 11-bit word format:

Word format (serial data)

11-bit Binary

Starting bit

1 digits

Data bits

8 digits

Parity bit

No parity bit

Stop bit

1-bit A

Communication data (information frame) format

Data formats:

Address Code

Function code

Data area

Wrong school Check


Data length:

1 bytes

1 bytes

N bytes

16-bit CRC code (redundant Loop code)


Note: 1, 1 bytes consist of 8-bit binary numbers (8 bit).

     2,ModBus is a registered trademark of Modicon Company.

     3,"From the machine" in this file is both NKB-20RX intelligence.

 1,Communication Information Transmission Process:

When the communication command is sent by the sending device (host) to the receiving device (from the machine), the transmission command is received from the machine that meets the corresponding address code, and the information is read according to the function code and related requirements, if the CRC is checked correctly, the corresponding task is performed, and then the execution result (data) is returned to the host. The returned information includes the address code, the function code, the data after execution, and the CRC checksum code. If the CRC checksum fails, no information is returned.

 1.1 Address Code:

       The address code is the first byte (8 bits) of each communication information frame, from 0 to 255. This byte indicates that the from machine where the address is set by the user will receive information sent by the host. Each machine must have a unique address code, and only the from 

machine that conforms to the address code can respond to the callback information. When the information is sent back from the machine, the callback data starts with their respective address codes. The address code sent by the host indicates the sender address to be sent to, while the address code returned from the machine indicates the return from the machine address. The corresponding address code indicates where the information came from.

 1.2 Function code:

      Is the second byte of each communication information frame transfer. The ModBus communication protocol can define a function code of 1 to 127. The NKB-20RX Intelligent Series instrumentation/transmitter uses only a portion of the function code. Sent as a host request, through the function code to tell what action should be performed from the machine. As a from-machine response, the function code returned from the machine is the same as the function code sent from the host, and indicates that the machine has responded to the host and has done the relevant action.

Table 8.1 MODBUS Partial function code

Function code


Operation (binary)


Read Switch quantity input

Read all the way or multi-channel switching status input data


Read switch volume output

Read all the way or multiplex switch output status data


Read Register data

Read data from one or more registers


Write Switch Quantity output

Control all the way relays "fit/split" output


Write a single-way register

Write a set of binary data to a single register


Write multi-channel registers

Write multi-set binary data to multiple registers

 1.3 Data area:

The data area includes what information needs to be returned from the machine or what action to perform. This information can be data (e.g. switching input/output, analog input/output, registers, etc.), reference addresses, and so on. For example, if the host tells the value of the register return from the machine through function code 03 (including the starting address of the register to read and the length of the read register), the returned data includes the data length and data content of the register.

For different machines, the address and data information are not the same (the Communication information table should be given). NKB-20RX Intelligent Series instrumentation/transmitter using Modbus Communication protocol, host (PLC, RTU, PC, DCS, etc.) using communication commands (function code 03), you can read its data register arbitrarily (its Data information table is detailed in the appendix).

 The data registers of the NKB-24RX Intelligent series instrumentation/transmitter store up to hundreds of kilowatts of electricity (e.g. current, voltage, power, 0~31 harmonic components, etc.), and are both 16-bit (2-byte) binary data, and high in front; the maximum number of registers to read at a time (the number of various types of electricity) is 50. The command format for NKB-20RX Intelligent response is from the machine address, function code, data area and CRC code. Data in the data area are two bytes and high in front (except for electrical energy).

 2,Introduction to MODBUS function code

 2.1  Function Code "03": Read multi-channel Register input

 For example, the host wants to read 32 from the machine register data with an address of 01 and a starting address of 0000. The address and data of the From machine (NKB-20RX Smart) data register are:

Message format sent by the host:


Host sending

Number of bytes

The information sent


From the machine address



Send from a machine with an address of 01

Function code



Read Registers

Start Address



Starting address is 0000

Data length



Read 1 Registers

CRC Code



CRC code calculated by host

 Message format returned from the machine (NKB-20RX Smart) Response:

From the machine response

Number of bytes

The information returned


From the machine address



From the 01 from the machine

Function code



Read Registers

Read the word



1 registers for a total of 2 bytes

Register Data 1



Measurement values

CRC Code



CRC code obtained from machine calculation




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