Thermal Flow Meter

摘要

A thermal flow meter capable of measuring flow rates of a gas flowing in a forward direction and a backward direction with a high degree of accuracy is provided. A thermal flow meter 300 according to the present invention includes a bypass passage configured to retrieve and flow a measurement target gas 30 received from a main passage 124 and a flow rate measurement circuit 601 configured to measure a flow rate by performing heat transfer with the measurement target gas flowing in the bypass passage. In an outlet port side chamber 4216 provided at an upstream with respect to an outlet port 352 of the bypass passage which is formed to be open in a downstream direction in a flow direction of the measurement target gas, a guide 4217 is provided to oppose the outlet port to change a direction of a flow of the measurement target gas flowing in from the opposite side, and the outlet port and an inflow unit of the outlet port side chamber are arranged to be eccentric when they are seen in a direction along the flow direction of the measurement target gas flowing in the main passage.

主权项

1. A thermal flow meter comprising:
a bypass passage configured to retrieve and flow a measurement target gas received from a main passage; and a flow rate measurement circuit configured to measure a flow rate by performing heat transfer with the measurement target gas flowing in the bypass passage, wherein the bypass passage includes: an inlet port which is formed to be open at an upstream side of the main passage; an outlet port configured to discharge the measurement target gas retrieved from the inlet port of the bypass passage to the main passage; a flow rate measurement passage unit provided between the inlet port and the outlet port and configured to measure a flow rate of the flow rate measurement circuit; and an outlet port side chamber provided at an upstream with respect to the outlet port of the bypass passage, wherein the measurement target gas retrieved from the inlet port of the bypass passage is measured by the flow rate measurement circuit at the flow rate measurement passage unit, and is thereafter guided to the outlet port side chamber, and is discharged to the main passage from the outlet port side chamber via the outlet port, and in the outlet port side chamber, the outlet port is provided to be open in a downstream direction of a flow direction of the measurement target gas in the main passage, and a guide is provided to oppose the outlet port to change a direction of a flow of the measurement target gas flowing backward from the outlet port to an upstream side of the outlet port, the outlet port and an inflow unit of the outlet port side chamber are arranged to be eccentric when they are seen in a direction along the flow direction of the measurement target gas flowing in the main passage.