DanW

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About DanW

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    instrument guy

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  • Location Midwest, USA
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  1. Analog Wiring NO NO

    OK.  I thought the distinction your were making was signal type (analog vs digital), not connector type (screw terminal vs terminal block).   Even so, given the number of times I've found the problem to be a whisker (that errant single strand) that makes it way out from under the screw terminal and touches where it shouldn't, I'd take a ferrule over bare stranded wire even if a fork is the correct and proper solution.   Have you encountered maintenance/performance-over-time issues with ferrules under screw terminals?n   Loosening?
  2. Analog Wiring NO NO

    I have the panel shop use twisted pair from the short run from field terminal blocks to the AI cards.  You can see the blk/clear pair below coming up from the top of the field terminal blocks. I haven't a clue why analog signals rate fork terminals and discretes rate ferrules.  What's the logic for that?
  3. Universal Analog Input Card

    It is not just a marketing term, there is a true functional difference between a dedicated function analog input card (4-20mA only) and a universal input card. An analog input card that takes a direct RTD or thermocouple input in addition to 0-10Vdc and 4-20mA has a lot of functionality that an analog input card that a 4-20mA-only card does not have.
  4. Honeywell HC900

      1.  Did the HMI ever communicate successfully with the CPU, or is this a commissioning/start-up problem? 2.  What HMI instruction faults the HC900 CPU? 3.  Which version firmware is the HC900 CPU running? 4.  Which hardware comm is for CPU/HMI comm?  Ethernet or RS-485? 5.  Is the HMI the Modbus Master, HC the Modbus slave? 6.  Are the CPU’s genuine Honeywell, or the fake, knock-off made in India models?
  5. Swimming Pool PLC

    If the pump doesn't pump water or the heater doesn't turn on and heat, then you need to determine whether the pump or heater is faulty or whether the control circuit that tells the pump to run or the heater to turn on can be the reason those things do not turn on and do what they're supposed to.  
  6. What performance factor is so critical that you'll travel 1/3 way around the world to find an alternative to what you're using now?  What does your current vendor suggest for upgraded performance? In answer to your question, I'm unaware of any standard of comparison.  But I can understand why - so much of PLC's performance is related to how it is programmed.  
  7. Rosemount Radar Level Transmitters

    > only when filling the water chamber. Is the radar positioned so it shoots through partially through the fill stream? Does the fill splash onto the antenna? Does the fill create turbulence like waves or agitation ?  Is the algorithm one designed for turbulence (which does not reflect the beam energy straight back up) ?
  8. Rosemount Radar Level Transmitters

    Water has a high dielectric so it should be a no-brainer application for radar, but non-contact radar is complex so the fault could be any of a dozens of reasons.    Diagnosis, remediation and root cause analysis require data.   Data for top mount, non-contact radar level includes stuff like - as complete a description of the fault/failure that can be compiled - accurate dimensional sketch or drawing or annotated photos of the installation with respect to geometry (slopes and angles) of the tank ceiling, nozzle, walls, interior structures and its fill/empty ports, radar mounting (angular aimers, flange/screw thread), antenna purge - written narrative on the process: temperature, pressure, atmosphere, mixing/agitation, -when, where and how it fills and empties, condition of the interior of the tank (steam?  dust?  rats?) - written record of the device model number, technology, beam angle, blanking zone distance for that device, range and accuracy - device's spec sheet and operating manual - written record of the existing setup (parameters, as found) - written report of device diagnostic log - screen shots of the echo profile at various levels - maintenance history - written notes on periodic inspections of the process side of the instrument - condition of the antenna for water, dust or material deposits - recorded trend charts of the level at a fairly high sample rate so that you can analyze the frequency, duration and time of the faults, to analyze whether the faults are event-related. A skilled (factory) technician with field experience for that manufacturer might be able to identify some probably causes and provide some remediation.  
  9. Fuel tank level automatic report

    see this thread covering the aspects of serial printing, then one adds the wireless on top.  It's a project. http://forums.mrplc.com/index.php?/topic/18102-slc-503-to-print-tickets/
  10. BACnet for running a site

    I've never used BacNet but if you're familiar with it, why not?  The alternative is probably Modbus, but why switch mid-stream if you'd had success with Bacnet in the past? I have seen several comments on Linkedin from those in the HVAC world who are migrating, when possible, to Modbus from Bacnet because of issues with inter-operability of Bacnet produc', but having to experience, I can't comment. If you consider Modbus, RTU over RS-485 has an inherent issue with grounding and might require an RS-485 repeater Isolator to eliminate ground loops between points at long distances, where the earth grounds are at different potentials.   Ethernet is inherently isolated by design, although the spec for distance is 100m, although the signal doesn't die at 100m, you're on your own as to whether it works and how well beyond that point, so people put in a switch as a repeater at 100m intervals.
  11. Honeywell Experion SCADA

    From experience 15 years ago with a SCADA version (Plantscape) of the DCS software, I feel fairly confident asserting that without a valid license code, Experion DCS software has no trial period at all therefore zero functionality; meaning that limitations are total.  I’m fairly confident that the software will not even install without a valid license code. 
  12. PT100 on Arduino Mega Industrial Shields PLC

    1.  The 4-20mA signal is converted to a voltage for the analog input on the Arduino to read it properly. Ohms Law says that 4.0mA current through a 250 ohm resistor drops 1.00 volts (E=I*R) 20.0mA current through a 250 ohm resistor drops 5.00 volts (0.20A * 250ohms = 5.0V) When 4.0mA current passes through 237 ohms, then the voltage drop is:   0.004A * 237 ohms =  0.948V. Not having exactly 250 ohms makes your reading low. 2.  You need to know what the scaling or range is for the temperature transmitter.    4.00mA = x Deg F or y Deg C 20.00mA = x Deg F or y Deg C 3.  Your calculations for what resistance is make no sense whatsoever.   > I got the values from an online pt100 table for resistance and tabulated them from 0-110C in 10 deg increments and for the corresponding resistance using:  nADC = 1023 * ( 237Ω/(237Ω+Rpt100)) The Arduino 'sees' only the mA current signal from the temperature transmitter and the voltage drop it creates across the analog input.   That signal could be relative humidiy, velocity, flow rate, pressure, temperature or about 100 other process variables. Your calculation has to interpret the voltage drop seen at the input and scale that voltage drop for temperature. You can only do that when you know for certain what the range of the temperature transmitter is (see item 2, above). 4.0mA = x deg F or C 20.0mA = x deg F or C. If you don't know, then you can estimate the range with freezing water and boiling water. Make up an icebath of crushed ice and a little water and put the RTD in the ice bath.  That's close to 0 deg C or 32 Deg F.   Measure the current output with a milliampmeter and record it. Boil water with the RTD in the pot.  Try to keep transmitter out of the heat.  Measure the current output when the water boils. Post the resulting current values here and I'll help you calculate what the transmitter is ranged for.
  13. OPC & PLC Integration

    I will freely make the statement that OPC UA will NEVER work with an unknown PLC with unknown data registers and unknown data properties. You can't even get OPC DA to work with an unknown PLC with unknown data registers and unknown data properties.  Hardware connection details do not qualify as data properties.   There is zero basis for accomplishing digital communications. The basis for data communication is to know and understand the properties of the field data and then create/use/buy a digital communications protocol and associated bus hardware to accomplish data transfer and whatever software/firmware is needed for data interpretation at the other end. The lack of understanding and knowledge about the data and its propertied precludes/exludes/eliminates the reasonablness of  attempting any type of digital communications. As to unreasonable expectations, I like the signature line of a water processing expert - "Any water can be made potable if you filter it through enough money".    The same applies to any task, but is it worthwhile compared to the alternative - outright replacement?  
  14. Temperatre Sensing

    Every yard sale I've ever been to has a box of junk including an old mechanical residential wall thermostat; probably working, just replaced with a programmed setback type. As long as the temperature range is adequate, then use a residential thermostat.  If the temperature range is outside that of a residential T-stat, there are dozens of cheap single loop temperature controllers with a relay output that will run on-off like a thermostat.   You'll need a foot of J, K, or T thermocouple wire, too.  All are powered devices, but so is your PLC.  Ebay is your friend. Many are sold by people who have no idea what they are, so it's up to you to know what you're buying.  You need to know how to decode the model number to make sure it has an electromechanical relay that you can use with your PLC DI. 
  15. A 32 bit floating point consists of four 8 bit bytes, each represented by two hexadecimal characters. The actual total value, 147082 (decimal) is 0x480fa2c0 in 32 bit floating point. the 1st byte is 0x48 the 2nd byte is 0x0F the 3rd byte is 0xA2 the 4th byte is 0xC0 The first byte value 0x48 makes a low 6 six digit value in the 100,000's in 32 bit floating point   substituting a value 0x47 for the first byte reduces the total to well below 100,000, down to 37811. Although there are four accepted formats for floating point word and byte order and most common issue in getting the correct value is getting the words and bytes in the correct order, the problem here is that the value you provided from the ladder logic has no byte value close to 0x48 to get a 32 bit floating point total into the range of 100,000. Your ladder logic value is 15598 17316  decimal 15598 converted to hex = 0x3CEE 17316 converted to hex = 0x43A4 None of those bytes is close enough to 0x48 to get you a total over 100,000.  In standard format, 0x3CEE43A4  = 0.029084988 Swapping word order gets the closest value: 0x43A43CEE = 328.476 Swapping bytes gets bizzare: 0x3CEE43A4  = 0.029084988 0xA443EE3C = -4.2485677E-17 Without a ladder logic value closer to what your actual total is, it's sheer speculation whether the issue is word/byte order.