基于单片机的智能低电阻测量仪 - 测试测量 - 电子工程
如图１所示，该仪器由5个部分组成：电源供应、精密恒流源、精2. 论坛推广：找兼职在各大论坛发帖。(这个我有经验)密电压放大器、A/D 转换器、单片机控制器。其主要技术指标如下：测试范围：0～20Ω0～200Ω0～2 k(三挡量程自动切换)；最高分辨力：0.001；测试电流：0.5 mA；测试精度：±（0.2%+2）；整机耗电：＜30 mA 。
整机采用6节5号镍氢电池供电（7.2 V）及通用DC/DC变换器，将电池电压转换成稳定的±5 V直流电压。该部分还有电池电压监测电路和充电电路，电池充满电 可以供仪器连续使用约50小时。
由斩波稳零运放做测试信号的同相放大，因为A/D转换器的满量程电压为2 V，测试电流0.5mA，对应20，200，2K 三个量 程的同相放大倍数为200，20，2。在负反馈回路接入两个由单片机控制的模拟电子开关SW1 、SW2，用于3个量程不同放大倍数 的切换：当量程为20 偈保琒W1，SW2均关闭；为200 偈盨W1开启；2k 偈盨W1，SW2均开启。仪器校验时应从低量程开始，否则不能校准所有的量程。另外，Ri，R1，R2， R3应选用精密电 阻和精密电位器，使温度的影响降至最低。
如图2所示，采用4 1/2位的ICL7135芯片，接成满量程为2 V的电压表 的模式。ICL7135用5位BCD码的形式向单片机提供数据，并提供过量程（OV）和欠量程（UN）信号给单片机用于量程自动切换。ICL7135的时钟频率来自T5（CD4060）的Q5端，频率为1.25 kHz，正好是工频50Hz的整数倍，能提高仪器抗工频干扰的能力。A/D转换频率约为：3.3次/s。T5的COUT端还提供4MHz的时钟频率给单片机。
本仪器最大特点是用软件实现自动调零和量程转换，省去故障率较高的电位器和量程切换 开关。软件调零的方法是：开机后单片机进行自检，如果系统工作正常就读取A/D转换的结果。当连续读取5个A/D转换结果后，判断它们是否都小于0.2Ω,否则，就认为操作者没有 将测试棒可靠短路，仪器继续显示调零提示符。如果连续5个值都小于0.2Ω,这时就找出其中最小值作为初始值，以后每次的测量结果都要减去初始值。?
根据A/D转换芯片ICL7135的过量程和欠量程信号，由单片机自动进行量程切换。量程切换 要 完成3项工作：首先是切换精密放大器的放大倍率，再是调整初值的有效位数，最后是调整 小数点的位置。PIC16C57单片机没有中断功能，采用查询的方法与A/D转换器通讯，利用A/D转换的间隙显示数据。PIC单片机与显示模块中的74LS164采用串行数据通讯，每次只显示1位数据，为防止显示 发生闪烁，刷新率紧接着还将推出Facebook版和Android版。我们已经迫不及待了。（(转自游戏邦)）Prototyping at Wooga: How to find the needle in the haystackby Antti HattaraBeing successful on mobile is no small ether you re a indie developer or a more established company, choosing the right projects to work on can be a demanding task.I lead the Pocket Studio at Wooga, where we re focused on making casual, mass-market ing in the business of making games, there s a seemingly simple way of telling if a prototype is a winner; is it fun?That sounds straightforward. But how do you evaluate this?While it s by no means a perfect recipe for success, a three-phase framework currently helps us evaluate our ase One: The PitchA new idea always starts with a person and the ideas themselves can come in many different me can be harder than others to explain, and at this stage it s usual that most ideas sound like they could have a lot of make the ideas more comparable we reduce them to a pitch line and a one-pager that communicates the core gameplay and the twist (or why it is unique, or better).It sounds short, but one page should be enough to successfully communicate the idea and why it s special. It also pushes you to think from the player s th the one pager a few things should be clear:Objective: Is it clear what we want to do/achieve?Opportunity: Does it sound appealing?Manageable scope: Does it have a well-defined and clear goal? An understandable spec?Desire: Is it appealing to work on? Is there potential for iterations?If there are several different ideas, this process helps us evaluate which adds the biggest twist or is the most unique and which has the biggest potential re s an example of something we moved forward with; a move-based, line-drawing puzzle game with re we could see that we d be testing the mechanic with levels, and that this would make it easier and faster to ase Two: The Prototype ScoringWith the prototype we re looking at two things; is it intuitive, and is it replayable?To find out if it is intuitive we do user testing. We want to confirm that the basics are in order, that the theme is exciting, and that there is an intuitive you are going for a mass-market game those are going to be tough to fix evaluate these you need to have reference benchmarks which can either be previous tests or tests done with a competitors game. One s sneakier than the other, but both e second step is to add some method of scoring into the game that sets the focus and gives you a rough, yet broad, overview of your game s strengths and weaknesses. It also introduces meaningful choice, essential for making a game th Jelly Splash we used level targets, and in Pocket Village we used ese both meant that players would come back, and with Pocket Village in particular, players would have to make choices that determine the course of their progression with limited moves or ase 3: CompetitionsBy this stage the aim should be to have a fun game that is approachable. In phase 3, our objective is to test The depth of design, and Extendability (i.e. get a sense of how much the game requires on the content side).A competition helps test the game with a larger amount of users and over a longer period of time. We used a Facebook group to source players to share their experiences and om here, we could measure engagement and a lot of players are dropping out at level 3, then chances are level 3 is too adding a 3-star scoring system enough to ensure people come back, or would a high score list be better suited to your game?These are all scenarios this stage should answer. If people simply aren t coming back, is it time to call it a day on this prototype?But if the third stage is successful, you might just be onto a mmaryThis is by no means a fixed recipe for success I wish!Tastes changes, players evolve and there is no sure fire bet in the app world. This approach has served us well so far, though, and sticking to the following three steps has already produced some interesting ase 1: The game should be well defined and appealing, i.e. the core and the twistPhase 2: Intuitive replayable, i.e. solid idea for fun via meaningful choicePhase 3: Engaging extendable, i.e. scalable and the design works for free-to-playThe examples used in this article for LINES have since turned into Jelly e game has passed every test we could throw at it, and so we announced it today on stage at Casual Connect SF will launch on iPhone and iPad on 15 August, shortly followed by the Facebook and Android versions of the game. We can t wait.(source:pocketgamer) 文章导航Previous Previous post: 手游和主机游戏研发应互相学习什么？下一条 Next post: 张柏芝、谢霆锋和王菲应大于30Hz 。程序流程如图3所示。
仪器与被测电阻采用4线制接线法，能消除接插件电阻的影响。此外，由于仪器分辨力很 高，所以要求测试夹具进行镀银处理，这一点很重要，否则会造成测试结果漂移不定。? 仪器批量生产的测试结果表明：仪器的技术指标达到设计要求，能够满足生产、科研的需 要。如果仪器稍加改进，可以当作高灵敏的直流电压表和电流表使用。安全期计算失误如何补救