Technical Information. Difference between ON-OFF and Analog output. Outline. How pressure is detected

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1 3 Outline The Pressure Switch detects of gases or liquids. Built-in circuitry allows for the adjustment of set points and s. Outputs are - solid state or reed switch type s. Some ls feature analog s. The is detected using solid state, metal diaphragm or piston type sensors. Applications for switches are numerous and include areas such as positioning, leakage testing, supply verification, etc. 3 Difference between - and Analog - - is also referred to as switch. Fig. () shows an equivalent circuit of a NPN switch with the off. In this circuit the load is not powered, because there is no current flow. Negative potential is not connected. When using a PLC, the input section sees a high level. 2 Solid state sensor This sensor is used in dry air and inert gas applications. Four diffused resistors form a bridge circuit on a silicon diaphragm. When is applied, the diaphragm is deflected causing the diffused resistors to change resistance (piezoelectric effect). An electrical signal, which is proportional to the change, is inputted during normal operation. Characteristics: Quick response Long service life Compact Stainless steel diaphragm sensor This sensor is used in humid air, water or oil. Four diffused resistors form a bridged circuit on a stainless steel diaphragm. All d parts are made of stainless steel. Pressure detection is identical to the silicon diffused sensor with the exception that the resistors are diffused on to the stainless steel diaphragm. Characteristics: Quick response Long service life Wide variety of applicable fluid Sensor voltage V How is detected V: Sensor voltage 4 diffused resistors forming a bridge circuit. Pressure P 4 diffused resistors from a bridged circuit on silicon diaphragm. P: Pressure Silicon diaphragm or stainless diaphragm When diaphragm is deformed by applying, resistance value of diffused resistor varies and therefore sensor does too, due to piezoelectric effect. As the increases, sensor voltage becomes larger. (Refer to the graph left.) Fig. () Equivalent circuit of a NPN type switch with the off Fig. (2) shows an equivalent circuit of a NPN switch with the on. In this circuit the load is powered. Besides, the input part of PLC becomes low level. PLC detects the signal change from high to low and then can proceed to the next process. The point at which the is switched is variable freely within the allowable setting range. For the -, there is a PNP type beside a NPN type. About the difference between NPN and PNP, refer to page Fig. (2) Equivalent circuit of a NPN type switch with the on Analog An analog provides an voltage that is proportional to the measured by the sensor. Output voltage (V) Pressure Rated voltage Absolute vacuum SEB/6B: [kpa] to [kpa] = to [V] PLC level 2 to 24 [VDC] Max. 3 [V] No current flow. is not powered. PLC level 2 to 24 [VDC] Max. 3 [V] Current flows. is powered. Analog Output Pressure Characteristic Graph 6-3-6

2 4 Technical Information 4 Difference between NPN and PNP NPN Fig. () Connection example of NPN PLC level 2 to 24 [VDC] Fig. (2) Equivalent circuit of an NPN switch with the off PLC level 2 to 24 [VDC] Fig. (3) Equivalent circuit of an NPN switch with the on PNP Fig. (4) Connection example of PNP PLC level 2 to 24 [VDC] 2 to 24 [VDC] Max. 3 [V] Fig. () Equivalent circuit of a PNP switch with the off NPN transistor PNP transistor No current flow. is not powered. Max. 3 [V] Current flows. is powered. Max. 3 [V] No current flow. is not powered. 2 to 24 [VDC] PLC level 2 to 24 [VDC] Current flows. is powered. Fig. () shows an example of a NPN switch. The solid state switch is an open collector. The NPN refers to type of transistor used. Fig. (3) shows the equivalent circuit with the transistor in its state. The current for the load flows in (sinks) to the transistor. The NPN type of is also referred to as the Sinking Type. In order for this circuit to work, the other side of the load has to be connected to the positive terminal of a power source. The diagram on the left shows two power sources, one for the load and one for the switch. In actual applications it will cause no problem to use one source for both. Summary: An NPN has the current flowing from the load into the transistor when energized. (Sinking type) (PLC uses the one for VaCOM.) Fig. (4) shows an example of a PNP switch. The solid state switch is an open collector type. The PNP refers to the type of transistor used. Fig. (6) shows the equivalent circuit with the transistor in its state. The current for the load flows out (sources) of the transistor. The PNP type of is also referred to as the Sourcing Type. In order for this circuit to work the other side of the load has to be connected to the negative common. Summary: A PNP has the current flowing from the transistor to the load when energized. (Sourcing type) (PLC uses the one for COM.) SE ISE PSE I SE3 PS I SE 2 SP ISA2 IS SM PF2 IF Data Fig. (6) Equivalent circuit of a PNP switch with the on 6-3-7

3 Hysteresis Hysteresis is the difference between the and value of an. This is necessary to prevent the switch from Chattering once the setpoint is reached. In the case of Normal Mode, the remains until the falls to a level below the setpoint minus the hysteresis. This means the will be turned off at a specific which can be calculated as follows: P (n) (n2) Hysteresis Hysteresis switch point = setpoint hysteresis Reversal Mode is defined as: switch point = setpoint hysteresis Normal Reverse 6 This is used when the has to stay within a certain range. The hysteresis is fixed (3 digits) (SEB/6B: 2 digits). When calibrating the switch, make sure that calibration point P is at least 7 digits different from calibration point. The effective area of operation is shown in the graph and is marked with L. If the difference between P and is less than 6 digits, this will not operate. In the case of a switch with 2 s, the Output 2 is using calibration points P3 and P4. Reversal Mode reverses above operation. Window Comparator Mode can be applied in situations where the supply has to be within a certain range. 7 Pressure Window comparator (n2) P (n) Window comparator L = Effective area H = Fixed hysteresis (3 digits) Peak high and peak low display s Peak high Peak low Under most operating conditions the will vary over time (see graph). The highest measured is stored and displayed as Peak Mode. The lowest measured is stored and displayed as Peak Mode. H H L Accuracy Pressure Switch Series PSE This is used when the has to stay within a certain range. The hysteresis for these switches is fixed at 2% F.S. The effective area of operation is shown in the graph and is marked with L. Thus, Series PSE can be set without paying attention to the difference between P and. (n2) P (n) Peak high Window comparator Normal Normal Reverse Reverse Caution: Motion differs only for remote controlled high accuracy switch series PSE. Refer to the right chart. /ISE3, /ISE4, 4B, 4E, /ISEB, 6B Pressure Peak low L = Effective area H = Fixed hysteresis (2% F.S.) Peak high and peak low display s for PSE Summary: Pressure fluctuations are constantly monitored and the maximum or minimum s updated. This function allows the user to record the quality of his regulation before performing any kind of calibration procedures. Applications include the control of in a caulking operation. H H L 6-3-8

4 6 8 Temperature characteristics Failure predict function The temperature characteristic is defined as the change in linearity over a given temperature range. All data given in a technical specification sheet is based on 2[ C]. The temperature range is dependent on the product series. Normally SMC products are rated from to [ C] or to 6[ C]. Analog voltage [V] Pressure indication [kpa] We explained by giving 2 examples. As for temperature characteristics, the smaller this value is, the smaller the error would be. That means it is strong against the temperature changes. 9 Repeatability The repeatability is defined as the ability of an instrument to provide the same every time for the same input. Usually given as a percentage of the full scale value. Example: Full scale reading [kpa] Setpoint for [kpa] Repeatability ± [% F.S.] F.S. = [kpa] [kpa] = [kpa] ± [% F.S.] = [kpa] x. = ± [kpa] The deviation from the setpoint is ± [kpa]. This means that the can become energized anywhere between 49 to [kpa]. (Refer to the chart below.) Note: If the switch allows an error of [% F.S.], the turns at [kpa]. Taking the repeatability into account, the turns at to 2 [kpa] and, in the same way, the display turns [kpa] at 49 to [kpa]. (Refer to the chart below.) Thus, the smaller the repeatability, the more precision in reproduction the product achieves. Actual [kpa] Normal [kpa] 49 Pressure In the meantime, will be turned. Rated Pressure 3 3 Pressure [kpa] Example) When the property at the temperature characteristic condition ±3. [% F.S.] and 2[ C] is expressed by the bold line in the chart on the left, how much temperature effect will the analog voltage receive? It can be determined. Example: Analog = to [V] F.S. = [V] [V] = 4 [V] ±3 [% F.S.] = 4 x.3 = ±.2 [V] The error induced by the temperature change can be as much as ±.2 [V]. Since this is the maximum value, the error will actually occur within the range enclosed by the thin line in the chart on the left. Example) When the property at the temperature characteristic condition ±3. [% F.S.] and 2[ C] is expressed by the bold line in the chart on the left, how much temperature effect will the analog voltage receive? The chart on the left illustrates the example when [kpa], F.S. = = [kpa], ±3.% F.S. = x.3 = ±3 [kpa]. It means that if the tempareture is changed within the range of to [ C], the error will occur at the max. ±3 [kpa]. Since this is the maximum value, the error will actually occur within the range enclosed by the thin line in the chart on the left. 49 Pressure indication Effective area of indication at [kpa]. In the case of performance decrement caused by clogging up the silencer of vacuum system (ejector), cracking of vacuum pad, or decreasing the vacuum reaching degree by leakage from vacuum piping, it detects the abnormality quickly and send out the to the outside right before the system comes to a stop. In case the - is in the normal, when the failure predict switches (over P), and the turns without reaching the failure predict (P3), the number of failure predict detection is counted. When it is consecutively counted up to the failure predict numbers (EC) preset, the failure predict will turn. When a switch turns, (over P) and the exceeds the failure predict (P3), the count of failure predict numbers will be reset. OUT Failure predict P3 P Failure predict number (EC) Since it is normal, the number count is reset EC =. Abnormal EC = Auto preset function Abnormal EC = 2 Output Abnormal EC = 3 Auto preset function enables automatic selection of the optimum set point value when the switch is used for adsorption confirmation simply by repeating the adsorption and release cycle with the workpiece. Refer to the catalog and instruction manual for how to enter the auto preset. This section describes calculation of the set value. How to Calculate the Set Value A = Max. value in auto preset B = Tentative min. value in auto preset P = A (A B)/4 = B + (A B)/4 Manual adjustment is possible after finishing in the auto preset. Starting Adsorption Adsorption Adsorption Finished Adsorption No adsorption Released Released Released Released NOTE: Make sure to generate a vacuum before calibration. NOTE: Make sure to continue vacuum vacuum when finished. Note) In the case of using this function on PSE, input the auto shift signal while workpiece is not adsorbed. Judging as B =, calibrate the set point value. A P B SE ISE PSE I SE3 PS I SE 2 SP ISA2 IS SM PF2 IF Data Effective area for switch to become energized

5 7 2 Auto shift function The auto switch function is the function to regard the value at the point of this signal being input as the benchmark and to display and conduct switching. For example, it will be used to take countermeasures against the main line fluctuation. If the main line is fluctuated, the performance of an ejector will vary and also the will cange at the non-adsorption case. Therefore, the phenomenon that switching is not done will take place, even if a workpiece is in suction. (Refer to the chart below.) The auto shift function is utilized like this case. Normal Supply normal Supply drop Supply increase Operating normally Not turned with adsorption Not turned with non-adsorption If the auto shift function is used, switching will be done by regarding the point of this signal being input as the benchmark. Therefore, switching can be surely done as long as the auto shift signal is being input at the nonadsorption case. And if the auto shift signal is input, the value at the benchmark will be defined to be on display. As such, the set value to be set at the time of confirming adsorption will be converted from the time when the auto shift signal is input. In case the auto shift is not at all used, switching is done just on the basis of either larger or smaller than the set value. Meanwhile, when the auto shift is used, switching will be done by whether to fluctuate by the set value from the benchmark (from the time of inputting auto shift). (Refer to the chart below.) Normal AUTO-SHIFT terminal P P Disconnected When the Auto Shift Function is NOT used. Supply normal Supply drop Supply increase Operating normally [ms] or longer P Operating normally P When the Auto Shift Function is used. Operating normally Another application for the auto shift function would be the testing for leaks. Under normal circumstances a vessel charged with compressed air to a certain will stay pressurized at the same level unless the vessel has a leak. If the vessel has a small leak the will decrease over time. No vessel is absolutely leakproof, therefore leakage testing is done measuring the amount of drop over a period of time. Using a switch, an can be generated as soon as the level decreases by [kpa], for example. Without the Auto shift function the vessel has to be charged to the exact level every time. If the initial level is too high the of the switch does not become energized at all or becomes energized after an excessive amount of time. If the is too low the is always energized. In either case it is impossible to determine if the vessel is good or bad. Filled Reverse n n2 Normal filled Insufficient filled Excessive filled When the Auto Shift Function is NOT used. To combat fluctuations in initial level, the auto shift feature is activated as soon as the vessel is charged. The initial level is now used as a reference. As soon as the drops by [kpa] (see example above) from the point at which the auto shift feature is activated, the is energized. Refer to the chart below. valuen Filled Set Reverse AUTO-SHIFT terminal n2 Disconnected Normal filled Insufficient filled n n2 n n2 Excessive filled When the Auto Shift Function is used. [ms] or longer 6-3-

6 8 How to Activate the Auto Shift Function Pull the AUTO-SHIFT input to for at least [ms]. The auto shift feature is activated by the rising flank of the auto shift input. The Display and Set points are now based on the at the moment of release after auto shift input. Example: The figure below is based on the condition of set values as P = 4 [kpa] and = 2 [kpa]. Actual (kpa) Display [kpa] AUTO-SHIFT terminal Disconnected - Operate in the manner same as ordinary since auto shift function is not used. [ms] [ms] [ms] Since auto shift signal is inputted at applying kpa, switching is done at s of 9 [kpa] and 7 [kpa]. After [ms] is passed, display is unstable around zero during the time exceeded. 3 Channel selection function Channel Selection Function is explained with an example when adsorbing workpiece. The on the nozzle varies according to the nozzle diameter. It is necessary to change the setting whenever changing the nozzle size in line. But in reality, it is impossible to stop the line only for change of nozzle. Pressure switches are required for each nozzle to change the without stopping the line. Channel Selection Function is adopted for that case. Normal of OUT2 (CH. B) P P3 P4 of OUT (CH. B) P Nozzle Replacement of nozzle Nozzle 2 P3 P4 of OUT (CH. A) Normal P Nozzle Nozzle : Large diameter Nozzle 2: Small diameter Abnormal operation It is also available for adjusting one nozzle to the different form of works. When there are two types of nozzles, OUT and OUT2 are adopted without any problems like OUT for Nozzle and OUT2 for Nozzle 2. When more than 3 types of nozzle are needed, A and B channels are available for selection; thus 2 s x 2 channels = 4 s are available. Nozzle 2 Nozzle 3 Nozzle 4 How to Select the Channel When the CH.SELECT terminal is open state, CH.A is selected, while when connecting with, CH.B is selected. It takes [ms] to switch the channel. Channel CH.SELECT terminal CH.B [ms] [ms] CH.A Disconnected of OUT2 (CH. A) Certain switching can be obtained by selecting the corresponding to the nozzle as the graph above. [ms] [ms] SE ISE PSE I SE3 PS I SE 2 SP ISA2 IS SM PF2 IF Data 6-3-

7 9 4 2-wire switch connections Voltage and current sensors A 3-wire type switch is a switch that has an line other than the positive and negative lines that supply the electricity. When there are 2 s, 4 lines will be required in total. This type of switch belongs to the family of 3-wire type switches. 2-wire type switches have only positive and negative wires that are used for supplying the electricity from the power source and for providing the as well. The 2-wire type works with both the sinking type (current runs into the switch) and the sourcing type (current is flown out of the switch). It is dependant upon whether a load is connected with the positive or negative side. These switches are known for high speed response, longevity, and they can reduce wiring work. Voltage signal is a voltage signal in the range of to [V]. The signal has to be converted by an A/D converter for display or switch. Current signal is a current signal in the range of 4 to 2 [ma]. The signal is transformed into a voltage signal before being converted by a A/D converter for display or switch. Advantages and Disadvantages (Long distance applications) When the voltage signal has to travel any amount of distance, voltage drops occur due to the resistance of the lead wire. The voltage drop increases proportional with the resistance of the wire and thus proportional with the length of the wire. Caution PS, PS The load current range for a PS and PS is between [ma] to 4 [ma]. If 4 [ma] is exceeded the transistor could be damaged. Besides, do not connect a PLC, which can detect [ma], since there is a leak current of [ma] in state. Connection example when used as a sinking type Brown Blue Brown Blue OUT(+) OUT( ) OUT(+) OUT( ) to 4 [ma] 2 to 24 [VDC] Connection example when used as a sourcing type Connection example with PLC Brown unit Switch Input Blue Connection example with NPN compliant, sourcing type input unit Input unit Switch NPN compliant Sourcing type Input unit Input Brown to 4 [ma] PNP compliant Sinking type Input unit Connection example with PNP compliant, sinking type input unit 2 to 24 [VDC] Sensor Sensor to [V] Current I Lead wire resistance r Current It may result in an error when the electric potential difference is caused between sensor s and of a receiver device. Connection of the voltage Current Voltage drops at the value of r x I. Connection of the current Equipment It appears that it would be of benefit to reduce the current flow as much as possible, however if the current is reduced too much other problems, such as inductive noise from external devices, occur. Result: Voltage s are not suitable for long distance applications. SMC s analog s are all of the voltage variety, but tests have proven that there is no problem in applications of [m] or less. Current is the same value. 4 to 2 [ma] Current I Lead wire resistance r Equipment The current flow is the same regardless of the distance. The cost of a current system is higher, because the voltage signal has to be converted to a current signal on one end of the transmission line, then on the other end it has to be converted to a voltage signal again. The packaging size of a current sensor might be larger due to the size of the additional parts

8 2 Technical Information 6 Protective construction 8 Operable fluids by switch for general purpose fluids 7 IP Second characteristic numeral First characteristic numeral First Characteristics: Degrees of protection against solid foreign objects Non-protected Protected against solid foreign objects of mm ø and greater Protected against solid foreign objects of 2. mm ø and greater Protected against solid foreign objects of 2. mm ø and greater Protected against solid foreign objects of. mm ø and greater Dust-protected Dusttight Second Characteristics: Degrees of protection against water Non-protected Protected against vertically falling water drops Protected against vertically falling water drops when enclosure titled up to Protected against spraying water Protected against splashing water Protected against water jets Protected against powerful water jets Protected against the effects of temporary immersion in water Protected against the effects of continuous immersion in water Pressure units conversion (Approximation) Ex. ) Convert the units of 3 [mmhg] to [kpa]. [mmhg] =.3332 x.3332 x x 3 = [kpa] Ex. 2) Convert the units of 8 [kpa] to [kgf/cm 2 ]. [kpa] =.97 x 2 [kgf/cm 2 ].972 x 2 x 8 =.876 [kgf/cm 2 ] Dripproof type Dripproof type 2 Sprayproof type Splashproof type jetproof type Strong jetproof type Immersible type Submersible type Example) In the case of stipulated as IP6, we can know the degrees of protection is dusttight and water jetproof on the grounds that the first characteristic numeral is 6 and the second characteristic numeral is respectively, that gives it will not be adversely affected by direct water jets from any direction. Pa (N/m2) x 3 x 6 x x 4.33 x x 2 Unit Stainless steel Metal exists in nature as ore (like oxide or sulfide). This means that oxide or sulfide is more stable than pure metal. Accordingly, metallic material chemically oxidizes (metallic constituent becomes ion and melts out). It corrodes in the natural environment. Even though corrosion of metal easily occurs in an environment where oxidizing tendency is stronger, some kinds of metal have a characteristic for which corrosion never happens if the level of oxidizing goes higher than a specific point. In such a case, it is called metal in passive state. Stainless steel has corrosion resistance because of a thin coat of passive state on its surface. However, there does not exist stainless steel with absolute corrosion resistance; therefore, many types of stainless steel have been developed for improved corrosion resistance performance. SMC Pressure Switch and Pressure Sensor for general purpose fluids have adopted stainless steel 34 for the fittings where in contact with fluids as well as stainless steel 63 for diaphragm of sensor part. Corrosion resistance performance of both stainless steel 34 and stainless steel 63 is almost the same level in anti-corrosiveness property. Caution SMC Pressure Switch and Pressure Sensor do not have explosion-proof construction; do not use flammable gases or liquids. Also, do not use toxic gases or liquids. kpa MPa bar kgf/cm2 atm mmh2o or mmaq mmhg or Torr x 3 x 6 x.97 x x 6.97 x 7.6 x 3 x 3 x 2.97 x x 3.97 x x 3 x.97 x x 7.6 x 3 x 2 x x.97 x x x.33 x x x x 2.33 x x x x x.3332 x x 4.39 x x x.38 x 3 x x 4.39 x 7.36 x x x 2 PSI.43 x 4.43 x.43 x 2.43 x.427 x.476 x.422 x x 2 SE ISE PSE I SE3 PS I SE 2 SP ISA2 IS SM PF2 IF Data 6-3-3