Flow Sensors

Flow Sensors Contents Technique and application for flow sensors Technique and application for flow sensors, amplifiers and compact models Terminology / Setting instructions Detection of microflow impulses Technique and application for flow sensors inline-digital display Ex area certification / Notes on safety applications Technique and application IO-Link, sensors with IO-Link Flow sensors Series 400 / Series 500 Probes Series ST / STK Probes high temperature 120 °C/160 °C Series ST Probes chemical resistant Series STA Compact models Series SC 440 / SCS 440 Compact models Series SNS 450 / SN...

Flow Sensors Technique & Application Function The function of the flow controller is based on the thermodynamic principle. The sensor is heated internally a few degrees °C compared to the medium into which it projects. When the medium flows, the heat generated in the sensor is conducted away by the medium, i. e. the sensor cools down. The temperature within the sensor is measured and compared to the temperature of the medium. The state of flow can be derived for each medium by the temperature difference attained. Areas of application for flow monitors Thermodynamic flow monitors function without...

Flow Sensors Technique & Application Probes The temperature-sensitive measuring elements are fitted in the tip of the probe. The probe tip and the adjoining thread/mounting part are made in one piece of stainless steel in many probes. This guarantees absolute tightness and high compressive strength. Special materials are used in corrosive, and particularly in oxidizing media, since stainless steel shows only limited resistance to corrosion in this application. In standard applications, probes can be mounted independently of the direction of flow of the medium. In any case, it is important to...

Flow Sensors Technique & Application NPT threads Flange types NPT threads can be provided as an alternative for all types which have a G1/2 or a G3/4 thread. NPT threads are conical and must be screwed into an equally conical counter-part. Two types of NPT threads must be distinguished. NPT thread according to ANSI B 1.20.1 does not ensure a good seal by itself and requires the use of a sealing medium, e.g. Teflon tape. It is not possible to use flat gaskets with this type of thread. Main applications are: • detection of small flow velocities in pipes with large cross section • mounting of the...

Flow Sensors Technique & Application Special materials Hastelloy B-2 (2.4617) belongs to the group of highly corrosion-resistant nickel-molybdenum alloys. This material has excellent characteristics in reducing media, e.g. in hydrochloric acid of any concentration and for a large range of temperatures. It can also be used in hydrochloric, sulphuric, acetic and phosphoric acid media. Good resistance against corrosion such as pitting, crevice corrosion, chlorine induced stress, corrosion cracking, hair-line corrosion, abrasion and corrosion within the heat influence zone allows for a large range...

Flow Sensors Technique & Application Amplifiers All amplifiers have a multicolour LED display which visually indicates the flow tendency. If the LED light is red, the preinstalled limit value is not reached and the switching output is not activated. The yellow LED indicates that the limit value was reached and the output is active. In addition to the yellow LED, 4 more green LEDs can light up to indicate how much the limit value is exceeded. For the installation of the amplifiers, make sure that the devices are not subject to heat build-up. The distance between adjacent devices should not exceed...

Flow Sensors Technique & Application Terminology Detection range Current consumption Start-up time The detection range of a probe or compact device indicates the flow velocities of the medium for which the probe can provide an analysable signal. If the medium is not specified, the details for water are applied. Because the different media have different thermal conductivity, the detection range as well as the temperature drift are also dependent of the respective medium. At the upper and lower limit of the detection range, the temperature drift is higher. The detection range does not limit the...

Flow Sensors Technique & Application Terminology and Setting instructions Switch-off delay The variable time delay which can be set between 0 and 25 seconds becomes active during flow standstill (drop-out delay). If the medium ceases to flow and the amplifier display indicates this state, the relay contact is actuated only after the set delay. During the delay period the yellow LED lights up together with the red LED. Cable break monitoring Cable break monitoring shuts off the flow monitor output if no probe is connected or if the probe cable has been severed. In case of cable severing, "flow...

Flow Sensors Technique & Application Setting instructions/Detection of microflow impulses Analog output Flow sensors with analog output supplies a current intensity which depends on the flow speed. The output current range is defined from 4 mA to 20 mA. The dependence between flow speed and output current is non-linear. The detection range is adjusted over two potentiometers: "Range" ( ) and "Adjust" ( ). The lowest value (>4 mA, 1st green LED) is set with the "Adjust" potentiometer at the smallest flow speed to be monitoring and the highest value (20 mA, 5th green LED) is set with the "Range"...

Flow Sensors Technique & Application Detection of microflow impulses/Inline-Flow monitoring Continuous switching signal The adjustable output switching signal extension can be set to a time which is slightly above the duration of the pulse and the interruption. When a pulse is detected in this setting it will cause an output signal which is maintained until the extension time has elapsed. Any new pulse detected during this period will restart the interval. For the period of time during which the pulses are detected in regular succession the device will generate a continuous signal which is only...