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Level Measurement System

Discussion in 'Electronics Homework Help' started by jenny1979, Dec 29, 2014.

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  1. jenny1979


    Dec 28, 2014
    A level measurement system on a water tank consists of a transducer with a sensitivity of 50 mV/m H2O, an instrumentation amplifier and a Programmable Logic Controller (PLC), all connected in series.

    (i) If the tank has a height of 5m and the input range of the PLC is 0 to 10 V what should be the gain of the amplifier?

    (ii) If the analogue input card on the PLC is running a 12 bit analogue to digital conversion, write the equation to rescale the signal back to m H2O.

    (iii) Draw a block diagram of the system showing inputs to and outputs from each block and the sensitivity of each block.
  2. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Um, since this is homework, have you actually read the book associated with this class? Also, Google is your friend. This is more a problem in critical thinking than anything else. Ask yourself these questions:

    What is the purpose of a transducer? You don't have to know how it works, just know what it does.
    What is a 12-bit analog-to-digital (ADC) converter? What does it do?
    What is a block diagram? How does it show signal flow?
    davenn and KrisBlueNZ like this.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Okay, I just read your profile page. Congratulations on trying to pick up where you left off in college. No matter how little you learned or remember from that experience, it's still better than starting from ground zero. And welcome to Electronics Point!

    Members here are more than willing to answer your questions when you get stuck, but we also expect a lot of effort on your part. Can you provide a little background information about where you think you are in terms of knowledge, skill, and experience with the electronics hobby? You posted in the Homework forum, so our responses are likely to be somewhat terse: many who post here do so with the expectation that they can get easy answers without doing any work. This is not Yahoo! Answers. We want to help you to learn, not spoon-feed you canned solutions.

    Over the Christmas Holidays I gifted a ten year old grandson with a Radio Shack Electronics Learning Lab Kit. without knowing the entire contents of the box. Several things impressed me, the price being one. However, it wasn't shrink-wrapped, so I could open the lid and give a cursory examination of the contents.

    First, the box contained two project workbooks, analog and digital, by noted practical electronics author Forrest M. Mims III. I grew up reading articles written by this man. His writing style is clear and succinct. He also has a website where you can purchase his books and beginner electronics courses. Note that the workbooks included with the kit do not have any (or very little) theory. They are project books that show you how to hook components together to accomplish some goal. You are expected to learn theory on your own from other resources. And of course you are free to build your own projects.

    Second, the kit includes a solder-less prototyping area that allows you to insert components and connect them with insulated hook-up wires. These were not available when I was learning electronics, but I own several of them today. Back in the 1960s I even used one to assemble a circuit that was incorporated into the customer's machine, without bothering to translate the bread-boarded circuit to a soldered assembly! But that's another story. Printed circuit boards were expensive then, had long lead times, required laborious lay-out procedures, yada, yada, yada. It worked, so I installed it hidden away in a dark corner of the equipment cabinet.

    Third, the lab has several useful components "built in" to the front panel: potentiometers, slide switches, push-button switches, a photo-sensor, an earphone jack, an analog current meter, etc. These are connected to the prototyping board by slipping insulated (but stripped on the ends) wires under spring terminals. Before I purchased this kit I assumed that was all there was to it. But on Christmas day Grandson Mic opened the box and we discovered a tray containing all sorts of components: insulated stripped wires of various colors and lengths, a large assortment of resistors, capacitors, diodes, transistors, and integrated circuits. Apparently everything needed to wire up all the circuits in the workbooks was included in the kit!

    The lab requires six AA cells (not provided with the kit), which are installed in a battery compartment on the bottom and connected in series, with taps brought out at each connection. Thus there is 1.5, 3, 4.5, 6, 7.5, and 9 volts available between top and bottom "rails" on the prototyping board. Sweet!

    The only thing "missing" from this beginners electronics learning kit is a digital multimeter. I recommend you purchase a 3-1/2 digit multimeter, if you don't already have one, to measure voltage, current, and resistance. If you can afford one that also measures capacitance, that will come in handy too.

    I must confess that my grandson was not yet ready for a kit of this sophistication. Perhaps his mother or his dad will sit down with him to help figure out how to read about and wire up the workbook circuits. As for me, I would have done anything to own a kit like this at his age. I intend to purchase one for myself, just in case Mik has any questions to ask me from Virginia Beach. Heh, heh. Highly recommended for adults and clever children.

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