Digitally Curious - A Vintage LCD Watch Blog

Digitally Curious - A Vintage LCD Watch Blog

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  • Friday, May 15th, 2009 - 2:28 pm
  • Casio JP-100W [509] Pulsecheck sensor watch

  • Today's watch is Casio's very first pulse sensor watch, the JP-100W.

    Commonly called the "pulse sensor" or "pulse meter" watch, the pulsecheck is one of my favorite (easily top ten) Casio watches of all time. As I walk through the features, I'll point out why I love this watch so much, even though it includes many of my pet peeves.

    The ubiquitous black resin case is formed into a very simple square shape. I personally like this shape over the round or penta/octagonal shapes found on other models. I particularly like the fact that most of the front real estate is occupied with functional items, with almost no wasted space.

    The large main display shows the day, month and date - along with the current time in 24H or am/pm format. The case front is also home to the pulse sensor and a pulse-mode button.

    The rest of the watch is rather simple, featuring a common stainless steel snapback with a rubber band attached by spring-bars. The band is poorly designed, which causes new bands to dig into your wrist. (Or perhaps it's how it sits on my particular wrist) Also the execution of this snapback makes it almost impossible to remove the caseback without scratching or denting the case. Even my new-in-box specimen has scratches on the caseback.

    AND, the caseback cannot be removed without removing the band... Annoying!

    The watch features several very unique functions. Let me walk you through each mode, starting with the pulsecheck function.

    The pulse sensor is the obvious highlight of this watch. And although it seems like a gimmick, it works so well that I consider this one of the best watch technologies. Yes, of course anyone can count and divide by 60, but this watch just makes it so simple and easy. It's like having a calculator watch. Of course anyone can add, but a calculator watch just makes it simple and easy.

    The pulsecheck mode is entered independently from the "mode" button by pressing the "pulse" button.

    Once in pulsecheck mode, you place your finger (usually your pointer) and wait until your sensor measures your pulse. If you do it right, you will see the pulse bar light up each time your heart beats. As this picture from the manual demonstrates, you have to put your finger just right, otherwise it won't work.

    So how DOES this work? The sensor is actually a photo (light) sensor. It measures the change in light transmission in your fingertips as hemoglobin flows through your veins. Yes that sounds crazy, but it actually works really well. Typically, it only takes 5~10 seconds for the pulse sensor to measure a very accurate pulse rate. In fact, it works well even for people who's pulses are hard to find on their wrist or neck.

    One time, I came down with a bad case of stomach virus and became severely dehydrated. I remember checking my pulse with this watch, and learning that I had a resting pulse of 100! Yikes! I wore this watch that day to make sure my pulse didn't spike even higher.

    Of course, Casio is quick to remind users that this is not a medical device. I agree, this is not a medical device. And I am NOT giving medical advice here.

    Because the sensor is light-based, you can trick the sensor if you flash light on it. Or just cover and uncover the sensor very quickly.

    Unfortunately it's not a very fun game to play, since the pulse calculator maxes out at a pulse of 299 beats/min. I guess no human hear is supposed to beat that fast. :)

    So what is the point of a pulse sensor..? Is it just a novelty? In my opinion, yes it is. BUT, Casio obviously put some thought into the application of this technology. I'll explain the special "jog" mode built specifically for this watch.

    The jog mode is quite complicated, so I'll just explain what it is intended to do. As far as I can tell, this feature is limited to sprint straining regiments. And as such, I can see how it would have been awesome to have this watch when I was in track in highschool.

    The following paragraphs are meant to explain the watch functions, BUT it is NOT exercise advice. I repeat, exercise at your own risk, and consult your doctor before exercising!

    Here's the scenario: You want to do some sprint training, which involves running 2 laps as FAST as you can, and rest for 30 seconds. Then run 2 laps as FAST as you can, then rest for another 30 seconds. And keep repeating until you repeat this 10 times (I remember doing this in track!)

    The 30 second rest is really designed to give your body enough "recovery" time so that you can run another 2 laps without collapsing. You want to give yourself enough rest to recover, but you don't want to rest so much that the running becomes too easy and your muscles get cold. But the 30 second recovery time isn't a scientific number, it's just some guess. With this watch, however, you can theoretically give yourself a good training regiment.

    In jog mode, whenever you stop the stopwatch, the watch waits 60 seconds and then sounds an alarm tone with a "pulse" reminder display, asking you to take your pulse. Whether or not you take a pulse measurement, the watch will send you that reminder every 60 seconds, for upto 10 reminders--or until you re-start your stopwatch.

    So here's how to train with this watch: you run a few laps, then stop and take your pulse. You wait until your pulse rate comes back down to a reasonable number (say around 80~90) you resume your run. Then you stop and wait until the pulse comes back down again.

    YES I know it's a bit complicated, but the technology is pretty awesome for a 1980's watch. :)

    Once again, I'd like to remind everyone that this is not a medical device.

    EDIT * I forgot to mention that the watch also has a pacer (metronome) function, which gives off a regulated beep--much like a musical metronome. You can set your own pace, and then run so that your strides match the beeps from the watch. Anyone who's done some serious running knows that it is very important to keep a steady pace! This pacer function is completely optional, and only beeps while the time is running in the jogging mode.

    In addition to those functions, there is the alarm, timer and stopwatch. The alarm mode has 3 independent alarms, each of which can be set as a daily alarm OR a weekly alarm.

    The shot above shows the alarm set for "every Sunday at 12:00." Unfortunately it cannot be set for "weekday" or "weekend," it can only be set for one day of the week, or every day of the week. So while novel, it has limited use.

    The timer can be set to 20 hours, making it quite useful. The stopwatch, on the other hand, is somewhat redundant. Its inclusion can only be explained by Casio's anticipation that people will not want their watch to make crazy noises when timing non-exercise activities.


    So that's it for the watch. Now, I want to talk about the box. For MANY years (late 80's and early 90's), Casio used this gray plastic box to ship their watches.

    These boxes are awesome because:

    1. They are compact and stackable

    2. The clear cover means you can display your watches AND protect them at the same time.

    3. The clear cover can be nested neatly behind the case.

    4. The manual holder on the back can hold your manual without folding it. (Although, unfortunately, the space doesn't always fit the manual exactly.)

    5. They feature a dust cover so that you don't scratch up your case or manual.

    6. The watch is securely held inside the case until the stand is removed.

    In my opinion, this is the best Casio box ever designed, and FAR better than the flimsy boxes currently used by Casio. I'll talk about the evolution of Casio watch boxes in an upcoming article.

  • Filed under: watch
  • Comments!
  • » Hi there.
    In your opinion, what are the relevant differences between the JP-100W & the JP-200W? (i own one of the latter. Btw that watch went into space on the wrist of a member of a space shuttle crew)
  • by: Andy, submitted Saturday, May 23rd, 2009 - 5:16 am
  • » Hey Andy,
    They are pretty similar, the biggest difference, in my opinion, is that the latter one has a built-in light. Also, I have found that the sensor on the JP-200W seems to work better, but that's mostly speculation.
  • by: admin, submitted Tuesday, May 26th, 2009 - 12:39 pm
  • » Hey man, great review!

    Before this watch, it had been over a decade since I had a Casio, but I ran into this model in a humble electronic store and fell completely in love. I was so happy with my purchase, I went back and bought the last one as well!

    I'm new to this whole Casio thing and wanted to ask you about opening the hatch in the back, because one of them didn't have a battery in it. I'm not sure how to go by it, and was wondering if you could just use regular household tools to pop open the hatch.
  • by: Hien, submitted Saturday, July 18th, 2009 - 1:32 pm
  • » Opening it is simple enough, you just need a small flat screwdriver. Replacing the battery should be done with a fine tool so that you don't break the battery clip. In a pinch, you can bend a staple from your stapler to achieve this goal.
  • by: admin, submitted Thursday, July 23rd, 2009 - 3:31 pm
  • » I love this watch. I bought this watch when it first came out under the Casio brand and later a second one with Timex brand. Identical, with the little blue square pulse check button. I've used it every day for what must be almost twenty years, as my everyday watch and my jogging watch. As a amateur archaeologist/rock art specialist I've worn it in the Australian outback, Negev desert, Kenya, India, and never a problem with it. It is very lightweight and simple to use. Sometimes the pulse check doesn't work well, but it usually does. I went shopping and can't find any brand with anything comparable. I would love to find another that still works.

    But alas finally this summer it stopped working well. I put in a new battery, adjusted the push button contacts, but only a blank screen.

  • by: James, submitted Sunday, October 25th, 2009 - 6:24 pm
  • » Thanks for your very well-written review...I appreciate the detail. For anyone who might be interested (Hi JAMES!) - There's an NOS on eBay* right now. I ran across it while looking for the Pulsemeter which was used in the film ALIENS. I like the design a lot, very clean.

    * I have not connection to the Seller, just thought I'd pass that on.
  • by: JANIS , submitted Saturday, December 26th, 2009 - 3:15 pm
  • » Please Tell me were i can buy one, I had one back in the 80's and loved it.
  • by: Robert Rubio, submitted Monday, January 11th, 2010 - 7:29 am
  • » I bought one of these watches in Japan when they were new for my wife and she loved it. However it went dead/blank after a couple of years so I bought another one. It worked a couple of battery changes before it also "died".
    My wife thought so highly of them so she kept them in a drawer and handed then over to me yesterday to finally throw them away after some 20 years...
    As nothing to lose I disassembled the dead watches (they are just snapped together so no screws but be aware of the minuscle springs!!). The display contacts with the clock PCB via 2 "rubber" contacts. I cleaned these with a cotton pin with some alcohol and put every thing together (ouch those small springs) and they both come to life again!!
    Guess if my wife was happy :-)
  • by: Ingemar, submitted Thursday, June 10th, 2010 - 11:36 am
  • » Hi, what kind of battery does this JP-100W use?
  • by: pinky, submitted Friday, February 11th, 2011 - 12:18 am
  • » I have one for more than 20 years and it has been with me on many trips, as the most reliable watch. How I have a Protrek, which beats the features of the JP-100W, but I still use the old one as a timer and alarm.
    I have one question - the rubber ring which makes the watch waterproof finally broke after so many battery changes. Does anyone know if it is possible to buy a replacement or a compatible one from a different model?
  • by: Vincent, submitted Saturday, May 28th, 2011 - 11:45 am
  • » 01/04/2012
    I have two JP-100s. One is the original Casio, Pulsecheck and the other is a Timex Pulsewatch. I purchased both on Canal Street in New York City in 1989 and 2009 respectively. I bave been able to get the Casio to work in all functions except I can not get the watch to beep upon depressing the buttons or upon a set Alarm, Jog/Pacer. Timer, Stopwatch or Puslecheck. Recently it did work but then it stop and the watch is silent. I have tried to lift the prong and spring on the left so I am assured they contact the back cover but have had no success. I even changed the battery and made the contact with a metal tweezers in the AC hole and the side of the battery but nothing has worked. Could the position of the adjusting button or other buttons be preventing the watch from sounding the beep?
  • by: Richard, submitted Tuesday, January 3rd, 2012 - 11:42 pm
  • » This Casio JP-100 watch has 2 tiny springs that can get lost. I lost one and now some of the functions don't work! Who might be able to supply me with one or two of those little springs? 5/30/2014
  • by: John D., submitted Friday, May 30th, 2014 - 10:24 am
  • » How wonderful to read your writeup on the Casio JP-100. I have many fond memories of this watch and just acquired one in good condition at a yeard sale. One thing you did not mention (very obscure) is that while swimming, and checking your pulse (at the edge of the pool between laps) it's important to have a little rag, towel, or paper towel there, to give the sensor & your finger a little drying wipe. Then the light goes through fine. What a wonderful, functional, vintage watch. I have a question--do you know what years this was sold? I'd like to get a ballpark on when I got mine (I'm not great at recapitulating history from memories…) Thanks much, and rock on!
  • by: Chrystos Minot, submitted Sunday, June 22nd, 2014 - 7:13 am
  • » I received this watch in 1980 as a gift, but it was army green. Do you know of that model? It was purchased by my Uncle, when he lived in Japan. I loved that watch!
  • by: Eric Tanaka, submitted Sunday, January 22nd, 2017 - 11:07 pm
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