GMA-M Series Modbus Bus-based Multi-Turn Absolute Encoder

short description:

GMA-M Series encoder is a Multi-turn bus-based Modbus absolute encoder, it can provide max 16bits sing-trun resolution, with options of housing Dia.:38,50,58mm; Solid/hollow Shaft Diameter:6,8,10mm, Output Code: Binary, Gray, Gray Excess, BCD; Supply Voltage:5v,8-29v; MODBUS is a request/reply protocol and offers services specified by function codes. MODBUS function codes are elements of MODBUS request/reply PDUs. The objective of this document is to describe the function codes used within the framework of MODBUS transactions. MODBUS is an application layer messaging protocol for client/server communication between devices connected on different types of buses or networks.

Housing Dia.:38,50,58mm

Solid/Hollow Shaft Dia.:6,8,10mm

Interface:Modbus;

Resolution:Max.16bits Turns, Single turn max.16bits, Total Max.29bits;

Supply Voltage:5v,8-29v;

Output Code:Binary, Gray, Gray Excess, BCD;

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Product Detail

1. Basic Product Parameters

Category	Description
Product Series	GMA-M Series Modbus Bus-based Multi-Turn Absolute Encoder
Encoder Type	Multi-turn Absolute Encoder
Resolution	Maximum 16-bit for single-turn; Overall maximum of 29-bit
Housing Diameter	38 mm, 50 mm, 58 mm
Solid/Hollow Shaft Diameter	6 mm, 8 mm, 10 mm
Output Code	Binary, Gray, Gray Excess, BCD
Supply Voltage	5V or 8–29V
Interface	Modbus (RS-485)
Maximum Frequency Response	300 kHz
Protection Rating	IP54
Certificates	CE, ROHS, KC, ISO9001

2. Electrical Parameters

Output Type	Consumption Current	Load Current	VOH	VOL
Open Collector	≤80 mA	40 mA	≥ Vcc × 70%	≤ 0.4 V
Voltage Output	≤80 mA	40 mA	≥ (Vcc – 2.5 V)	≤ 0.4 V
Line Driver	≤150 mA	60 mA	≥ 3.4 V	≤ 0.4 V
Push Pull	≤80 mA	40 mA	≥ (Vcc – 1.5 V)	≤ 0.8 V

3. Mechanical Parameters

Parameter	Value/Description
Starting Torque	4×10⁻³ N·M
Maximum Shaft Loading	Axial: 29.4 N; Radial: 19.6 N
Maximum Rotational Speed	3000 rpm
Weight	160 ~ 200 g

4. Environmental Parameters

Parameter	Range/Description
Operating Temperature	-30℃ ~ 80℃
Storage Temperature	-40℃ ~ 80℃
Protection Rating	IP54

5. Communication Parameters

Parameter	Description
Transmission Interface	RS-485 (supports address range 1–254; default address is 01)
Baud Rate	Options: 4800, 9600 (default), 19200, 38400
Medium	STP (Shielded Twisted Pair)
Data Frame Format	1 start bit, 8 data bits, 1 even parity bit, 1 stop bit; no flow control

6. Modbus Message Format and Command Details

6.1 Basic Message Format

Command Type	Master Request Format	Slave Response Format
Read Location Value (03H)	Address \| Command (03H) \| Parameter Address \| Data Length \| Check Code	Address \| Command (03H) \| Byte Length \| Parameter Values \| Check Code
Preset Current Position Value (10H)	Address \| Command (10H) \| Parameter Address \| Data Length \| Byte Length \| Parameter Values \| Check Code	Address \| Command (10H) \| Parameter Address \| Data Length \| Check Code
Write Parameter Value (06H)	Address \| Command (06H) \| Parameter Address \| Parameter Value \| Check Code	Address \| Command (06H) \| Parameter Address \| Parameter Value \| Check Code

6.2 Example Commands

Read Location Value Example

Master Request:
01H 03H 00H 00H 00H 02H C4H 0BH
(01H: Address; 03H: Function Code; 00H 00H: Register Address; 00H 02H: Data Length (unit: word); C4H 0BH: CRC Check)
Slave Response:
01H 03H 04H 01H F4H 00H 01H 7BH FDH
(01H: Address; 03H: Function Code; 04H: Byte Count; 01H F4H 00H 01H: Location Data; 7BH FDH: CRC Check)

Parameter Setting Examples

Master Send:
01H 10H 00H 4AH 00H 02H 04H 00H 00H 00H 00H 77H E0H
Slave Response:
01H 10H 00H 4AH 00H 02H 60H 1EH
Note: Register address 004AH is used for setting the current preset position value; data length is 2 words (4 bytes, arranged from high to low).
Master Send:
01H 06H 00H 46H 00H 01H A9H DFH
Slave Response:
01H 06H 00H 46H 00H 01H A9H DFH
Note: Register address 0046H is used for counting direction (High byte fixed at 00H; low byte: 00H indicates clockwise [data increasing], 01H indicates anticlockwise [data decreasing]).
Master Send:
01H 06H 00H 45H 00H 04H 99H DCH
Slave Response:
01H 06H 00H 45H 00H 04H 99H DCH
Note: Register address 0045H is used for baud rate setting (High byte fixed at 00H, low byte represents the baud rate parameter).
Master Send:
01H 06H 00H 44H 00H 02H 48H 1EH
Slave Response:
02H 06H 00H 44H 00H 02H 48H 2DH
Note: Register address 0044H is used for ID setting (High byte fixed at 00H, low byte represents the device ID).

Change Device ID (Change ID from 01H to 02H)
Change Baud Rate (Set baud rate to 38400bps, parameter 04H)
Change Counting Direction (Set to anticlockwise, i.e., parameter 01H)
Set Current Position Value (For example, set to 00000000H)

7. Parameter Setting Registers

Register Address	Parameter Name	Data Length	Data Description
0044H	Device ID	0001H	High byte fixed at 00H; low byte represents the device ID
0045H	Baud Rate Setting	0001H	High byte fixed at 00H; low byte represents the baud rate parameter (see parameter table below)
0046H	Counting Direction Setting	0001H	High byte fixed at 00H; low byte: 00H indicates clockwise (data increasing), 01H indicates anticlockwise (data decreasing)
004AH	Current Preset Position	0002H	Four bytes (arranged from high to low); sets the current encoder position (do not exceed physical limits)

8. Parameter Table (Baud Rate and Counting Direction Options)

Baud Rate Options

Parameter Code	Baud Rate	Note
01	4800 bps
02	9600 bps	Default baud rate
03	19200 bps
04	38400 bps
05	115200 bps

Counting Direction Options

Parameter Code	Counting Direction Description
00	Clockwise: Data increases
01	Anticlockwise: Data decreases

9. Additional Information

Communication Data Frame Format:

1 start bit
8 data bits
1 even parity bit
1 stop bit
No flow control

Packaging:

The encoder is packaged in standard export packaging or as per buyer’s requirements.

Delivery and Logistics:

Lead Time: Shipment is made within one week after full payment is received.
Logistics: Delivered by DHL or any other courier as discussed.

Application Fields:

Widely used in various fields of automatic control and measurement systems, such as machinery manufacturing, shipping, textile, printing, aviation, military industry, testing machines, elevators, etc.

Product Features:

Vibration-resistant, corrosion-resistant, and pollution-resistant.
Can serve as a cost-effective equivalent replacement for well-known brands such as Sick, Heidenhain, Nemicon, Autonics, Koyo, Omron, Baumer, Tamagawa, Hengstler, Trelectronic, Pepperl+Fuchs, Elco, Kuebler, etc.
Gertech provides equivalent replacements for many international mainstream encoder models.

Selection Process (Five Steps):

If you already use encoders from other brands, you may provide the model information, and our engineers will recommend an equivalent replacement.
Determine the encoder type: Incremental, Absolute, Draw Wire Sensors, or Manual Pulse Generator.
Choose the output format (e.g., NPN, PNP, LINE DRIVER, PUSH PULL for incremental encoders) or interface (e.g., Parallel, SSI, BISS, Modbus, CANopen, Profibus, DeviceNET, Profinet, EtherCAT, Power Link, Modbus TCP).
Select the encoder resolution: Maximum 50,000 ppr for Gertech incremental encoders; Maximum 29-bit for Gertech absolute encoders.
Select the housing diameter and shaft diameter of the encoder.

Minimum Order Quantity (MOQ):

The MOQ is 20 pieces (lower quantities are acceptable, but the freight cost will be higher).

Production Lead Time:

Samples: 3 days
Mass Production: 7–10 days

After-Sales Service:

1-year warranty and lifetime technical support.

Agency and Cooperation:

Special pricing, market protection, and full support are provided for agency partners.
To become a Gertech agency, please send us an inquiry and our team will contact you promptly.