Model PFLOW3000 Series MEMS Mass Flow Sensors (VA.0)

MEMS Mass Flow Sensor The PFLOW3000 series of mass flow sensors are made with the micromachined (MEMS) sensing elements that ` offer an innovative thermal sensing principle with excellent linearity and removal of gas sensitivity of some common gases. This PFLOW3000 Series mass flow sensor series offer a fully customizable flow dynamic range of 100:1 with the full-scale flowrate from 2 SLPM to 50 SLPM. The sensors are opted with digital (I2C or RS485) and analog interface, with an operational temperature range of -10 to 55 °C. SPECIFICATIONS Performance characteristics (Test conditions: Vcc =...

Electrical Characteristics (Test conditions: Vcc = 8-15VDC, Ta = 20°C, RHa = 30…70%) Item Supply voltage Supply current Warmup time (4) Minimum Output load (analog & digital version) Response time (digital, analog) Output (analog) (5) Analog null voltage Analog null drift Maximum output (6) Output (digital) I2C bus voltage I2C frequency Resolution digital output Digital null offset Digital null drift (7) Note: 1. SLPM denotes standard cubic centimeters per minute. Standard conditions: 20°C, 101.325kPa, dry and clean air. 2. Accuracy is the combined error from offset and span calibration, linearity,...

PRESSURE DROP CHARACTERISTICS The product is designed for low-pressure loss. The major drop in the pressure is at the manual valve structure. The following graph illustrated the pressure losses of the selected models. Table 1: PFLOW3003 pressure loss Flow rate (SLPM) Table 2: PFLOW3008 pressure loss Flow rate (SLPM)

MECHANICAL DIMENSIONS Figure 3: PFLOW3000 dimensions with BSPT (R1/4”) connectors. All units are in mm Figure 4: PFLOW3000 dimensions with one-touch connectors. All units are in mm

Figure 5: PFLOW3000 connection and cable GAS CORRECTION FACTORS Gas type Correction factor To obtain the real flow rates in a specific gas, multiply the readings from the sensor by the gas correction factor in the table. The factors are approximate and should be used as guidelines only. Sensor performance strongly depends on gas dynamics and has to be evaluated in the respective application.

TYPICAL OUTPUT (ANALOG OUTPUT) Analog Output Table 3: PFLOW3000 typical analog output Flow rate (SLPM) Typical Analog output (Vdc) 4.9 Figure 6: PFLOW3000 typical analog output Digital Output Table 4: PFLOW3000 typical digital output Flow rate (SLPM) Typical Digital output (SLPM) 1.1FS Figure 7: PFLOW3000 typical digital output

DIGITAL RS485 Modbus COMMUNICATION The digital communication protocol is based on standard Modbus RTU Half-plex mode. A master (PC or PLC) can communicate with multiple slaves (the current product) for data exchange and communication parameter configuration. Refer to ELECTRICAL INTERFACE for cable connection. Hardware connection The RS485 hardware layer is TIA/EIA-485-A, as illustrated below. In this configuration, the product (PFLOW3000) is a slave. Communication parameters The PC UART communication parameters are listed in the following table. Parameters Baud rate (Bits per second) Start bits...

Frame The frame function is based on the standard Modbus RTU framing: Start_bits T1-T2-T3-T4 4 periods bit time, for a new frame. The address can be set from 1 to 247 except for 157 (0x9d). 0 is the broadcast address. Function codes: Define the product's functions/actions (slaves), either execution or response. The address of the register, length of data, and the data themselves. CRC verification code. The low byte is followed by the high byte. For example, a 16-bit CRC is divided into BYTE_H and BYTE_L. In the framing, the BYTE_L will come first, then followed by the BYTE_H. The last one is...

Serial number Serial number of the product (R) Flow rate Current flow rate (R) Baud rate Communication baud rate (R/W) Digital filter depth Response time or sampling time (R/W) Offset calibration Offset reset or calibration (W) Write protection Write protection of selected parameters (W) The detailed information of each register is described below: Y: enabled; N: disabled Write Y Address 0x0081 Read Y Description Address of the product Value type UINT 16 Values from 1 to 247 except for 157 (0x9d). Notes The broadcast address is not enabled, and the default address is 1. SN, Serial number Description...

GCF Description Value type Notes Response time Description Value type Notes Offset calibration Description Value type Notes Write protection Description Value type Write Y Read Y The gas conversion factor for applicable gas is different from calibration gas UINT 16 The GCF of air is 1000 (default), normally read from register 0x008B. Note: The product will disable this function with write protection once the metering gas is confirmed with the proper GCF. For a specific GCF value, please contact the manufacturer. 0x008B Write Read Digital filter depth setting UINT 16 0 ~ 9 programmable, corresponding...

DIGITAL I2C COMMUNICATION I2C interface connection diagram I2C interface command description Command Width (Byte) Command Name Filter depth Reset the offset of differential pressure Sensor serial number Flow rate Gas correction factor (GCF) Notes Int 16. bit 0 is the R/W flag bit; bit 1 ~ bit 7 are available; bit 8 ~ bit 15 = 0. The default I2C address is 1. Hex: 0x0002 (write) /0x0003 (read), Bin: 0000 0000 0000 0010 (write) 0000 0000 0000 0011 (read). Int 32/1000 SLPM The gas conversion factor for applicable gas is different from calibration gas. Int 16, 0 ~ 9, corresponding to 20 ~ 29 data...

CRC checksum calculation The 8-bit CRC checksum transmitted after each two data bytes (int 16) is generated by a CRC algorithm. Its properties are listed in the following table. To calculate the checksum, only these two previously transmitted data bytes are used. Property Name Protected data Width Polynomial Initialization Reflect input Reflect output Final XOR Example Value CRC-8 I2C read and write 8 bits 0x07 (x8 + x2 + x + 1) 0x00 False False 0x00 CRC (0x4E20) = 0x6D I2C interface read/write sequences