Abstract: A heat-conductive stream pipe has an upstream side and a downstream side temperature-sensing element having resistance wires wound round the pipe at a certain distance there-between to assure that there will be no thermal influence with each other. A control means controls a bridge circuit including a ground point at one end and a connecting point at the other end of each of the temperature-sensing elements so as to keep the temperature difference between the upstream side and the downstream side temperature-sensing elements at a constant level. An adjustable auxiliary heater is placed on the stream pipe at the downstream side near the downstream side temperature-sensing element. The mass flow of the fluid is determined by the voltage measured at the connecting point of the downstream side temperature-sensing element.

Abstract: A calorimeter comprises a laminar flow type flowmeter for measuring the volume of flow of a fuel gas as a value proportional to the difference between the pressures of the laminar flow elements and a stream pipe serially connected to the laminar flow type flowmeter to create a laminar flow therethrough. The stream pipe is provided with a heating means, a temperature sensing means for detecting the difference between the temperatures of the fuel's flow to and from the stream pipe portion heated by the heating means, and a thermal-type flowmeter for measuring a mass flow proportional to the differential temperature sensed. A computer unit calculates the outflow pressure and the volume of flow of the fuel gas in its normal state from the measured values of the absolute pressure, the differential pressure and the temperature of the fuel gas flowing into the laminar flow-type flowmeter and calculates the calorific value of the fuel gas as a value that is negatively proportional to the differential pressure.